O’Neill, ó Neill A Gaelic surname meaning descendants of Niall. The meaning of the personal name Niall is uncertain. The most famous bearer of the name was Niall Naígiallach (‘of the Nine Hostages’), ancestor of the Uí Néill. Adopted by several septs, the principal septs being located in Tír Eoghain (Tyrone). A sept of the Cineál Eoghain, who became Lords of Ulster after they defeated the Mac Lochlainn (McLaughlin). Their territory Tír Eoghain, comprised the present Tyrone and south Derry. A sub-sept the Clann Aodha Bhuidhe during the fourteenth Century settled in Antrim, in an area now known as Clandeboy. A sept in Thomond (Thuas Mhumhan) of Dál gCais origin, who were Chiefs of Clann Dealbhaoith in the barony of Bunratty in the present Clare. A sept in Leinster, whose territory was Magh-dá-chon now the parish of Moyacomb in the barony of Rathvilly in Carlow and extending into the barony of Shillelagh in Wicklow, also called Farren O’Neill. A sept of Déise which settled in the south of Tipperary. In 1890 O’Neill was the tenth most numerous surname in Ireland, the estimated number of bearers was 29,100, and the surname was found in nearly every county in Ireland. It was principally found in Dublin, Antrim, Cork and Tyrone. In the United States O’Neal is the 540th most numerous surname with anestimated 60,500 bearers, O’Neill is the 768th most numerous surname with an estimated 44,000 bearers, and O’Neil is the 978th most numerous surname with an estimated 33,000 bearers. It is numerous in the states of Connecticut, Delaware, Maryland, Massachusetts, New York, and Pennsylvania. In England and Wales in 1996 it was the 207th most numerous surname.