The History of

the Brennan Name

In modern Ireland there are many Brennans: the name comes twenty-eighth in the statistical list of Irish surnames. Here and there one is met with the prefix O, but to-day the form MacBrennan is seldom if ever found. The simple form Brennan is used in the anglicized form of two quite distinct Gaelic Irish surnames, viz. O Braonain and Mac Branain. The former is the appellation of four different unrelated septs; the latter of one only. Judging by the present day distribution of the name, two of these five have survived in large numbers in the districts around their original habitats. It is sufficient, therefore, just to mention en passant the three others which were located respectively in counties Galway, Westmeath and Kerry. Mac Branain was chief of Corcachlann, the old name of a territory in the eastern part of Co Roscommon: a succession of these chiefs appear in the Annals between 1159 and 1488. While the leading members of the sept retained the Mac until the submergence of the Gaelic order in the seventeenth century, the substitution of O for Mac, in some cases, is noted as early as 1360. The present day Brennans of Counties Roscommon, Sligo and Mayo, however, are nearly all MacBrennans, or more correctly MacBrennans. The principal O'Brennan sept was that of Ossory: they were chiefs of Ui Duach (mod. Idough) in the northern part of Co. Kilkenny. Their influence naturally waned as English power became paramount in Leinster, and though several O'Brennans retained some portion of their former estates, the seventeenth century reduced many of them to the status of rapparee - indeed, several famous or notorious bands of tories in Leinster were led by Brennans, and in the next century, one of the most intrepid and chivalrous of all Irish highwaymen, James Freney, was, he asserted, instructed in his calling by the last of these tory Brennans. The most distinguished of the sept was Most Rev. John Brennan (1625-1693), Bishop of Waterford and Archbishop of Cashel, friend of Geoffrey Keating and Saint Oliver Plunkett: though constantly the object of special attention from priest-hunters, he was elusive enough to remain continuously in his dioceses which he administered with marked wisdom, and his periodical reports to Rome are of the greatest value to the historian of the seventeenth century. Another John Brennan (1768-1830), popularly called the "wrestling doctor" and well known in his day for his satires on Dublin doctors, was also of the Ossory sept of O'Brennan and considered to be chief of the name. Among exiles of the name we may mention the Abbe Peter O'Brennan who was executed in 1794 for his resistance to the French Revolution.