Rooney, ó Ruanaidh, ó Rúnaighean Rooney is an anglicisation of a number of different Gaelic septs. A Gaelic surname meaning descendant of Ruanaidh (hero). A sept of Down who were based in the parish of Ballyroney, north of Rathfriland. ó Ruanaidhín, descendant of Ruanaidhín (diminutive of Ruanaidh) of Donegal and north Leitrim. ó Rúnaighean of Sligo. ó Maolruanaidh, meaning a descendant of Maolruanaidh (follower of Ruanaidh). A sept who prior to the Maguires were lords of Fermanagh. This is usually anglicised as Mulrooney but sometimes as Rooney. In 1890 Rooney was numerous in Leitrim, it was also to be found in Dublin, Down, Antrim and Mayo. The estimated number of bearers was 5,331. In the United States Rooney is the 2,158th most numerous surname with an estimated 16,500 bearers, and Roney is the 3,683rd most numerous surname with an estimated 8,250 bearers.