Irish Family Research Discover the secrets of your ancestors’ past Brendan Mullins Genealogist


      First Selected Surname:    

     Ó Cléirigh  -   O’Cleary   -   Clarke

       Clarke is an English surname, however, in Ireland the name was very widely used as the Anglicised version of Ó Cléirigh. There is no doubt though that some English Clarke settlers came to Ireland, but these are widely believed to be just a very small percentage. One of these, a protestant, arrived in Dublin with Cromwell in 16498. The surname O’Cleary is another Anglicised version. It is widely believed that the name Ó Cléirigh is derived from the word ‘cléirich’ meaning a clerk or cleric and it is from this that the name Clarke originated. As I have not yet located any of my Clarke ancestors from outside Dublin, I cannot say from whom they are descended.

     Cléireach lived in the ninth century and he was born about 820 A.D. He was descended from Feargal Aidhne, and his grandfather, Guaire Aidhne, both Kings of Connaught in the seventh century and his descendants can be located in the Annals of the Four Masters. They are accompanied with dates, but those that are pre 11th century cannot be fully guaranteed to be correct, even with two of the Four Masters, Brother Michael Ó Cléirigh and his cousin Cucogry Ó Cléirigh, being distant descendants as well. Brother Michael’s birth name was Tadhg an Sleibhe Ó Cléirigh and he took the name Michael on entering the Franciscans.

     They ruled in Uí Fhiachrach Aidhne, in the southeast area of Galway around the Gort area from about 900 A.D. until about 1280, when they were driven out by the Norman, William de Burgo. They moved to the barony of Tirawley in Co. Mayo, with minor branches later moving to Briefny O’Reilly in Co. Cavan and Kilkenny. They remained in Tirawley, in an area situated about two miles southwest of Ballina, until about 1345 when the majority of them were driven out and the main sept moved to Tír Conaill in Co. Donegal. It is known that a small number of them managed to stay in Tirawley until about the year 1500. (Interestingly, in Griffith’s Valuation in the mid 19th century there were 286 Clarke properties in Mayo).

     Cormac Ó Cléirigh who was a scholar, married the daughter of Ó Sgingín, ollam to Niall Garbh Ó Domhnaill in Donegal and their son, Giolla Brighde, succeeded to the office of ollam9. His descendants continued in this post for a few generations. They lived in Kilbarron castle which was built on the edge of the cliffs in the Bay of Donegal10.  The literary family of Ó Cléirigh, including Brother Micheál Ó Cléirigh, descended from these, and many of them became poets and antiquarians11. Also among these was Seaán Buidhe Ó Cléirigh in the 15th Century, who was the main scribe for ‘The Book of Potterlerath/Leabhar an Rátha’, (also referred to as ‘The Book of the White Earl’. This Earl was one of the Butlers, -James, 4th Earl of Ormond, who had become strongly gaelicised12.

     The surname, Ó Cléirigh, was one of the earliest to be recorded, dating from the middle of the tenth century13.   

     The first to use the surname was Flann, who was also known as Maolcerarda Ó Cléirigh14.   It is not certain that he ceased using the name Flann and became known as Maolcerarda Ó Cléirigh, but this may have been so. He is described in the Annals of the Four Masters as Lord of South Connaught and he was slain by the ‘men of Munster’ in the year 950 A.D., although this information, at this early period, should be taken with caution.                                                                                                                                      His father was Maolfabhaill, of whom the same annals describe as Lord of Aidhne and he died in 887 A.D.      

     The son of Flann/Maolcerarda Ó Cléirigh was Comhaltan Ó Cléirigh, who was Lord of Hy-Fiachrach Aidhne. He is described as a powerful chieftain who, in 964 A.D. with Maelseachlainn MacArcdai defeated the then King of Connaught, Fearghal Ua Ruairc, and slew 700 of his people15. He died in 976 A.D.                                                                                                                                      He was succeeded by Giolla Cheallaigh Ó Cléirigh who, in 998 A.D. slew Diarmuid MacDunadhaigh, lord of Siol Anmchadha, but in 1003 A.D. he himself was slain in a large battle against the Chief of Hy-Many, Tadhg Ó Ceallaigh16.

     The following chart shows eight generations including Cléireach, the source of the surname, and Flann, the first to use the surname. All titles and dates are from ‘The Annals of the Four Masters’.

8 R. C. Clarke, ‘The Remarkable Mr. Clarke’, Irish Genealogist, Vol. 5, page 130. Nat. Library of Ireland, Dublin

9  Robert Welch, The Oxford Companion to Irish Literature, Oxford Univ. Press, 2001, First Ed. 1996.

10  Rev. John Healy, ‘Kilbarron Castle and the O’Clerys of Donegal’, The Irish Monthly, 1879, Vol. 7, pp.1-11.

11  A. B. Clery, ‘The Muintir Cléirigh of Tirawley’, The Journal of the Royal Society of Antiquaries of Ireland, Vol. 75, June 1945, pp. 70-75.

12  Art Cosgrove, ‘A New History of Ireland, Vol. II, Medieval Ireland 1169-1534’, Second Edition 2005, First Pub. 1993, Clarendon Press, Oxford, pp. 692-693 and 801-803, NLI, Dublin

13  Edward MacLysaght, Irish Families, Fourth Ed. 1991, First Published 1957, Irish Academic Press, D 4, p. 56

14 John O’Donovan, Editor, The Annals of the Kingdom of Ireland by the Four Masters, Dublin 1851, Vol. 2, p.667, NLI, Dublin

15  Annals of the Four Masters, 2, p.688, NLI, Dublin

16  O’Donovan, Genealogies, Tribes and Customs of Hy-Fiachrach, pp 391-398

Tirawley KILLALA BAY The Barony of Tirawley, Co. Mayo

     For the next seven generations, just names without any dates or information, can be found in any of the annals, which bring us to about 1280 A.D., when the Ó Cléirigh’s were driven out of their territory in the southeast of Galway by De Burgo and into Tirawley in north Mayo where they remained until about 1345 A.D.

Part view of Clarke Shop on Patrick Street A partial view of the Clarke  Shop on Patrick St., Dublin Anne Clarke My grandmother, Anne Clarke 1883 - 1970 James Clarke My great grandfather,  James Clarke 1849 - 1907


born about 820 A.D     



Lord of Aidhne   died about 887 A.D.


Flann, also called Maolcerarda Ó Cléirigh

Lord of Connaught   slain about 950 A.D


Comhaltan Ó Cléirigh

Lord of Hy-Fiachrach Aidhne died about 976 A.D.


Giolla Cheallaigh Ó Cléirigh

........................................(second son to succeed father).........................................      Lord of Hy-Fiachrach Aidhne   slain about 1003 A.D



Cugaela Ó Cléirigh

(grandson of Comhaltan Ó Cléirigh

...........................Lord of Hy-Fiachrach Aidhne  died about 1025 A.D.......................                                             

.Braon Ó Cléirigh

slain about 1033 A.D


Eoghan Ó Cléirigh

 died about 1063 A.D.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     

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