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"Lug's forgotten Donegal kingdom": A book about the Ó Dochartaighs ancestors, the Síl Lugdach tribe.

Updated: Feb 26, 2019

Researching the early history and formation of our Clann is fascinating to me, particularly because it’s a part of our history which hasn’t been as well researched. This early period is represented in the medieval genealogies of the Ó Dochartaighs which go back to Dochartach son of Maonghaile son of Fiamhan son of Cenn Fáelad son of Garbh son of Rónán son of Lughaid. From other literary sources we know that before our Clann adopted the hereditary surname Ó Dochartaigh, we were a part of what was called “Clann Fiamhan”, in reference to the name of Dochartach’s grandfather Fiamhan. While conducting more research, I’ve recently learned that prior to that designation, our ancestors were identified as the Síl Lugdach tribe of northwest Donegal. The word Síl, a shortened form of Cenél, is an Irish word meaning “offspring” or “kindred”. Thus, the Síl Lugdach tribe, according to tradition, bore their name to denote them as the descendants of Lughaid son of Sédna son of Fergus son of Conal Gulban son of Niall of the Nine Hostages.

During the course of my research, the book, Lug's forgotten Donegal kingdom: The archaeology, history and folklore of the Síl Lugdach of Cloghaneely, has come across my radar a number of times. After Zack Daugherty, co-administrator of the Doherty Surname DNA Project, and I were talking about some of the apparent disconnects between the earliest portions of the medieval Irish genealogies and the modern Y-DNA haplotree (the ancient human family tree which has been literally encoded in our genetics), I ended up ordering the book from my library. One of the perks of working at a college and being friends with the library staff is that I can call them anytime and they can get almost any book I need from anywhere. They’ve worked very hard to get me literally scores of books over the last few years in the researching my own line of the family history and now that of our Clann—one of which had only three copies in libraries across the globe. A huge “Thank you” shout-out to Debbie Young and all the other staff at Rutland Library!


Lug’s forgotten Donegal kingdom was published 2012 by Dr. Brian Lacey, one of the most imminent archaeologists and historians in all of Ireland today. Dr. Lacey, who has lectured at universities, curated museums, and led the Discovery Programme (Ireland’s archaeological research institution), examines the history of the Síl Lugdach who were the ancestors of the two most powerful Donegal families: the Ó Donnells and the Ó Dohertys. In his book, foreworded by our very own Professor Charley Doherty of University College Dublin, Dr. Lacey does an exhaustive examination of the sparse archaeological and historical evidence that exists for that period (600-1100 AD). He believes this evidence paints a slightly different picture than the long-told traditions of our ancestry hold and offers a well-developed and thought-provoking alternative interpretation of that evidence.


The thesis of his work is that the ancestors of the Ó Dochartaighs and the Ó Donnells, the Síl Lugdach tribe, were not a part of the Cenél Conaill (descendants of the legendary prince Conal Gulban), but were in fact a separate tribe entirely. He uses clues preserved deep within place-names, local folklore, and Irish mythology—in addition to inconsistencies between the Irish annals and genealogy manuscripts—to show that the name “Síl Lugdach” likely refers to the tribe's ancient devotion and desire to be connected to the mythological pagan deity “Lug”—Lugh Lámhfhada—and that they were not truly genetic descendants of the Lughaid mac Sédna mentioned in the Cenél Conaill genealogies. Lugh, the father of Cú Chulainn, was a prominent character in Celtic mythology. Portrayed as a youthful warrior hero, his epithet Lámhfhada meaning “of the long arm” likely referred to his skill with a spear, or perhaps his abilities as a ruler.


While Dr. Lacey’s research turned up little concrete evidence for our Síl Lugdach ancestors, he identified a number of entries which certainly referred to them in the Irish annals between the years 870 to 1106 AD. He also believes prior to their use of the dynastic name “Síl Lugdach” they were referred to in an entry in the Annals of Tigernach for the year 614 AD as the "Luigni", a tribe who allied with the Cenél nEoghan against the Cenél Conaill in the battle of Sliabh Tuath. He points out that the Síl Lugdach were mentioned as a people distinctly identified and completely independent of either the Cenél Conaill or Cenél nEoghan, not a branch of the descendants of Conal (Cenél Conaill) as the medieval genealogies state.


Dr. Lacey says "It is almost certain that these people [the Síl Lugdach] originated in the Gort an Choirce and An Fál Carrach area of northwest Donegal” near Tullaghobegly. He uses the plethora of place-names that include the name Lug, the abundance of local folklore regarding him, and other evidence to back this up—including remnants of Lug's cult that have survived down to the modern day. For instance, Tullaghobegly, now re-associated with a (perhaps mythological) Saint Begley, was up until the 1300s AD referred to as Tulach Logha, meaning “the mound(s) of Lug". At the base of beautiful Mount Errigal, Donegal’s highest mountain, a location in the southeast corner of the original Síl Lugdach territory, is a place called Dunlewy—it’s Irish name “Dun Luiche” means “The fort of Lug”. Even one of the central places of their homeland, Gort an Choirce, mentioned earlier, meaning “Field of Oats”, has, in it's name, ties to Lug through the festival of Lughnasa a Celtic celebration of the harvest.


After the Battle of Almu in 722 AD, when their neighboring tribes were defeated, the Síl Lugdach began to expand eastward from their Tullaghabegley homeland. Not far into their new territory, at a place called Cloughaneely is the Clogh-an-Neely stone. Fanciful legend associates the large white stone as the deathplace of Lug’s father MacKineely, and the place-name spelling, which has been corrupted to mean the “Stone of MacKineely,” has been inscribed into the memorial pillar upon which the large white stone has been elevated.

Dr. Lacey points out that the correct historical spelling of this place name is given in the Annals of the Four Masters (for 1284 and 1554) as “Cloch Chinnfhaolaidh.” Cloch Chinnfhaolaidh is from the Irish words meaning “Stone of Cenn Fáelad.” Lacey believes that this stone was named for the first Cenn Fáelad, the father of Fiamhain and great grandfather of our Ó Dochartaigh progenitor Dochartach. He calculated from the genealogies that our Clann's ancestor Cenn Fáelad died sometime around the early-mid 700s, which aligns perfectly with the timeframe in which our ancestral tribe, the Síl Lugdach, are believed to have begun the expansion of their territory eastward. Dr. Lacey believes that Cenn Fáelad may have been the conqueror of this adjacent territory for the Síl Lugdach and that the stone which still remains to this day memorializes his conquest and the annexation of this territory to the homeland of our ancestors.

Later that century, after the Cenél nEógain defeated the Cenél Conaill at the Battle of Clóitech in 789, as the Síl Lugdach grew in power, they continued to expand, now into the old territory of the Cenél Conaill—particularly into the Kilmacrennan area and on into Raphoe. This is confirmed as the Annals of Ulster record that Máel Dúin (son of the second Cenn Fáelad of the Síl Lugdach) died in 817 AD as the prinnceps or "superior" of Raphoe, "a member of Colm Cille’s community”. By 870 the Annals give Dálách, the Síl Lugdach ancestor of the Ó Donnell Clan, the title of "chief of Ceneil Conaill", though Dr. Lacey argues that it is unlikely that he belonged to the Cenél Conaill a true genetic way (Dálách was the 2nd cousin, twice removed, of Dochartach).

Shaw's maps respectfully reproduced from Dr. Lacey's book showing the expansion of the Síl Lugdach (in green).


But how was Dálách of the Síl Lugdach also associated to the Cenél Conaill when the two tribes are referred to as historically independent tribes and enemies over the previous centuries? Dr. Lacey offers, in explanation, that the genealogies were reconstructed after the fact for political and social reasons. He says that “little [written record] survives from before the seventh century,” but that “Donegal is among the area from where we get the very earliest records for the history of this country”, particularly, he points out, because of the influential monastery at Iona, founded by Donegal's St. Colm Cille during the 500s. Lacey continues that Iona was among the earliest places that began the practice of keeping ‘annals’.

Prominent scholars show that the memory of oral tradition preserve genealogies accurately for an average of six, but no more than nine generations. This equates to 200-300 years of accurate history. Lacey says the enormously extensive Irish genealogies were “kept 'up to date' among various polities and kingdoms" before they were written down in these new monasteries in the early medieval times and were subject to "accidental change and deliberate manipulation". He continues that the genealogical schema for the periods earlier than this six-to-nine-generation oral memory during the time of the genealogies were being written down—rather than being a true genetic family tree—actually represent the later political affiliations "as seen by an 8th century genealogist", as they (the learned researchers of their day) tried to make sense of their history and society with the best information they had.


Lacey shows how after the Cenél Conaill were defeated in the battle of Clóitech and subsequently forced out of eastern and northwest Donegal, the church at Kilmacrenan likely lost its patronage. Lacey conjectures that the clerics at Kilmacrenan may have "accidentally or deliberately 'discovered'" a genealogical connection between the new powers expanding into the region, the Síl Lugdach, and the church's original supporters, the then-defeated Cenél Conaill. If his conjecture is correct, he says such as discovery would have proved a mutual benefit to both parties, bringing the conquerors on board as supporters of the church, while lending an opportunity to our Síl Lugdach to claim the "rightful" title of the kingship of the Cenél Conaill to ultimately rule all of Donegal. It also offered the Síl Lugdach prominence with a close familial tie to Colm Cille, one of the most venerated saints in Ireland. Thus the Ó Donnell and Ó Doherty, whom Lacey believes had no real genetic connection to the Uí Néill (the tribes such as the Cenél Conaill and Cenél nEoghan), due to the work of the clerics at Kilmacrenan, are now associated with them in historic tradition.

As our Síl Lugdach ancestors voluntarily converted to Christianity sometime after its arrival in Ireland, over a period of several centuries the cult of Lug was suppressed and ultimately eliminated. This newly discovered “connection” now explained the name of their tribe in a way which was acceptable to Christianity, as being descendants of the Lughaid mac Sédna of the historically powerful Cenél Conaill—rather than referencing an almost forgotten historic devotion to the pagan “Lug”, whose name had by that time seemingly been wiped from their memory, excepting what remained in a few place-names and stories. The rest is history. The Síl Lugdach, now ruling under the name and authority of the Cenél Conaill continued expanding eastward throughout Raphoe. Ultimately the Ó Donnell expanded south toward Donegal Town by around the year 1200 and the Ó Doherty expanded north to Inishowen by about 1350.


Dr. Lacey admits that the DNA study conducted in 2006 by Trinity College Dublin, in opposition to his theory, appears to confirm a genetic connection between the medieval Irish genealogies of the Ó Neill, Ó Donnell, Ó Doherty, and other clans who were claimed to have descended from the 4th century Irish warlord Niall of the Nine Hostages. This 2006 study was based on based on Y-chromosome STRs, however, a type of genetic marker which has over the past few years been understood to be more accurately used for confirming genetic connections within a period of a few centuries ago. More recent understandings in Y-chromosome DNA have identified SNPs (not STRs) as being more accurately insightful into the “deep ancestry” of these ancient and early medieval times. As Zack Daugherty and I were talking, contrary to the 2006 study, the data from the Y-chromosome genetic family tree (or SNP haplotree) as understood presently appears to indicate this common ancestor of the Uí Néill was much further back in time than the semi-legendary Niall of the Nine Hostages was supposed to have lived. The most recent developments in genetic genealogy seem to support the hypothesis of Dr. Lacey, that the Síl Lugdach were not as closely related to the Cenél Conaill, but perhaps they shared a common ancestor in the era before Christ.


Dr. Lacey's work offers a well-thought out alternative to the traditional histories which appears to be a plausible explanation. While it's mostly based on conjecture, almost any study from that era simply must be in light of the sparse amount of actual evidence remaining from over twelve centuries past. As the study of genetic genealogy continues to develop, I hope that established historical research institutions will take up the baton from the 2006 study to conduct further formal research in light of the new developments in the understanding of genetic genealogy. If we learn of anything, we will definitely keep you posted.

The direct paternal lineage of the Ó Dochartaighs may not come down from Niall of the Nine Hostages and his son Conal Gulban, from whom descend the Cenél Conaill, as legend has it. However, Dr. Lacey and other historians indicate, with a critical examination and commonsensical approach, that there is much less reason to doubt most of the genealogies back to around 2-3 centuries prior to their being written down. This means that the Ó Dochartaighs direct paternal genealogies likely have no serious objections back to the period of our progenitor who flourished around the 800s or 900s, Dochartach the son of Maongal son of Fiamhan son of Cenn Fáelad.

Would I like to believe the Ó Dochartaighs are descended from the renowned "High King of Ireland" Niall? Sure I would! Do I believe we are? Well, I like to look at things with a critical eye toward a search for accurate history, so I’m somewhat skeptical of accepting the legends as-is. Regardless of whether the direct paternal lineage of those bearing the Doherty/Dougherty name stems from this dynasty, it's statistically guaranteed that, if they existed, we surely have many ancestral ties to that "royal" line of the Cenél Conaill via the wives of our many Ó Dochartaigh and pre-Ó Dochartaigh ancestors. With that said, and the fact that these anecdotes of our ancient ancestors have been preserved within our Donegal traditions for over a millennium, I still enjoy and retell the stories that form our historic Ó Dochartaigh identity. Throughout the future, we will attempt to bring you a combination of both the traditional stories and accounts of our heritage, as well as critical analyses of them through the eyes of modern historic and scientific discoveries.

By the way, if you would like to purchase a copy of the book, visit Four Courts Press (Dr. Lacey's publisher),, or your favorite book seller. Happy reading!

Ár nDúchas,

Will Dougherty III

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Zack Daugherty
Zack Daugherty
Feb 25, 2019

Very interesting stuff! I've read about Dr. Lacey's work on this (I don't have a copy of the book though but I should). The only likely ancestor I have confidence in down to present day based on what I see with Y-DNA and surname clustering is Síl Lugdach. That being said I'm not really seeing much for Ó Donnells being represented within the haplotree as they should be at this time. It would be so interesting to have the database sizes grow another 10-fold; especially with more testers from Ireland.

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