The Irish surname Mahone is an anglicized form of the Gaelic name  Ó Mathghamhna meaning “descendant of Mathghamhain,” a name meaning “good calf.” Mathghamhain, forefather of the great Mahoney clan, was the son of Cian and Sadhbh (daughter of Brian Boru, 4th Century High King of Ireland). The tract of land, over which his descendants held sway, extended from Cork to  Mizen Head, and the Mahone chiefs were referred to in ancient Irish annals as "Rithe na Naoi bFonn" - Kings of the Nine Territories. Chief Diarmuid Mor O'Mahony  assumed the leadership of the Fonn Iatharach or Western Territory early in the 11th Century, and in the course of time, his people built twelve castles, the best known of which are Rosbrin, Ardintenant, Dunmanus and Dun Locha (near Mizen Head).