The Sionnach/Ó Sionnaigh (Fox) clan were chiefs in Kilcoursey, referred to as Muinter Tadgain, which also included
Clonlonan barony in
Westmeath. They were kings of
Tethbae (Westmeath) before they
surrendered it during the
Tudor conquest of Ireland. In the early centuries of Christianity in Ireland, the family were known as Ó Catharnaigh (O'Kearney in the Anglicized form), from their chief, Tadgh O'Catharniagh, who died in 1084. Tadgh's extraordinary cunning had earned him the nickname "An Sionnach", which translated as "The Fox" in English. Subsequently, the Catharnaigh branch acquired this nickname as a distinct surname. The influence and power of the Foxes declined, due to conflict with rival Gaelic monarchs, and advancing control of English forces. However, even when their influence had diminished, they still retained considerable territory in
Offaly, and became Barrons of Kilcoursey. The Mac Amhlaigh (MacAuley) sept are also cited as holding a portion of the Clonlonan barony. ==List of settlements==