Was St. Malachy O'Morgair an O'Dochartaigh?
Several texts on St. Malachy of Ireland, the archbishop to whom is attributed the controversial "Prophecy of the Popes" (Catholic Encylopedia, 1913, YouTube) mention that those of St. Malachy's surname, O'Morgair, changed their surname to O'Dougherty:
From the book The life of Saint Malachy O'Morgair (archive.org): "Malachy, or according to the Irish surname, Maol-Maodhog O'Mungair or O'Morgair§ was perhaps born at Armagh, in the year 1093 or 1094." Footnote: § "This family name was afterwards changed to O'Dougherty."
From the book St Bernard Clairvaux's Life Of St Malachy Of Armagh (archive.org): "Our Malachy, born in Ireland,  of a barbarous people, was brought up there, and there received his education… His parents,  however, were great both by descent and in power, like unto the name of the great men that are in the earth." Footnote  "... Therefore we may accept Colgan's statement that the family was known as O'Dogherty in his day (Trias, p. 299)..."
While there is more academic examination in the above-mentioned footnotes, below we can see the above-referenced excerpt from the Irish Franciscan friar John Colvin's Trias Thaumaturga, etc., published at Louvain in 1647. Colvin states that the family descended from nobility and anciently known as O'Morgair in his present day now bore the name O'Dochartaigh (Trias Thaumaturga, etc. at Google Books). Notice the word "Dochartinorum" which combines the Irish word "Dochartaigh" with the latin "-orum" meaning "of the".
The Cultural Heritage Project says the O'Morgair name is now obsolete and was not an early form of Ó Mordha / O'Moore (AskAboutIreland.ie). A poem attributed to St. Malachy himself (see pp. 185-187 of The life of Saint Malachy O'Morgair at archive.org) gives his father as being named "Diarmait" (Anglicized "Dermot"). On this note, it's interesting to note that a little over a century before St. Malachy's birth the death of another Diarmaid / Dermot was recorded. The Annals of the Four Masters and the Annals of Ulster record in that Diarmaid / Dermot, the son of Dochartach (progenitor of the O'Dochartaighs), who was the abbot of the monastery on Devenish Island, died in 972A.D. My initial thought was that abbot Diarmaid macDochartach would've been celibate, but it was actually well over a century after Diarmaid macDochartach when, incidentally, it was St. Malachy, himself, who instituted regulations concerning celibacy in the ecclesiastical order in Ireland (St. Malachy's Parish). With that said, in St Bernard Clairvaux's Life Of St Malachy Of Armagh, Dr. Lawlor analysed and accepted the earlier statement of Colgan that those who had bore the O'Morgair name were now known as O'Dougherty and further commented that,
"They had probably only resumed an earlier surname: for according to MacFirbis (Royal Irish Academy ms. 23 P. 1, p. 698) Malachy was of the same stock as St. Mael Brigte, son of Tornan. The latter, as well as the O'Doghertys, were of the race of Conall Gulban (Adamnan, Genealogy opp. p. 342)." (archive.org)
In her article, St. Malachy the Irishman: Kinship, Clan, and Reform, published in Proceedings of the Harvard Celtic Colloquium, Vol. 5 (1985), pp. 103-127 (JSTOR), Dorothy C. Africa refers to MacFirbis' manuscript as saying that St. Malachy came from the Síl Lugdech, the sept descended from Luighdheach son of Seadna, whom O'Clery gives as the 4th great grandfather of Dochartach. She further indicates that the origin of Colgin's knowledge about those of the O'Morgair name at that time bearing the name Ó Dogherty likely came from Ó Mulconry who served as the confessor of Hugh Roe Ó Donnell during his 1607 flight to Spain, where Ó Mulconry instigated Phillip III to found the College of St. Anthony in Louvain, where just a few decades later Colgin published his Trias Thaumaturga, etc. in 1647.
The O'Clery Genealogies give the primary lineage of the Ó Dochartaigh chiefs as descending through Dochartach's son Maongal. Could it be possible that St. Malachy came from an early branching-off of the Ó Dochartaighs, descended from Dochartach through his other known son Dermot the abbot of Devinish? The evidence is inconclusive, but we do know from the Ó Dochartaigh DNA study that there are a number of lineages which split off before the primary group of Ó Dochartaigh testers was developed. An interesting possibility to say the least!
Other Sources COMING SOON.