Quinn is an Anglicised form of the Irish Ó Coinn. The latter surname means "descendant of Conn". The surname Quinn is also rendered Ó Cuinn in Irish. The surname is borne by numerous unrelated Irish families in Ulster and the Irish counties of Clare, Longford, and Mayo. The most notable family of the name are that of Thomond, a Dalcassian sept, who derive their surname from Niall Ó Cuinn who was slain at the Battle of Clontarf in 1014. This family was formerly represented by the Earls of Dunraven. Another family is that seated in Annaly, who were related to the O'Farrell lords of Longford. Other families include one seated in Antrim; one seated in Raphoe; and one called Clann Cuain, seated near Castlebar. In the seventeenth century, the surname Quinn was common in Waterford. In 1890, the surname was numerous in Dublin, Tyrone, Antrim, and Roscommon. Quinn is one of the twenty most common surnames in Ireland. It is sometimes said that the surname Quinn is borne by Catholics whilst Quin is borne by Protestants.