Coole is based upon the ancient territory of Cuil, which was frequently referred to as the residence of the O'Cassidys (Irish: Ó Caiside). The O'Cassidys became the head physicians of the Maguires, and the territory was a collateral or dynastic branch of the Maguires. In the Annals it appears as Cuil na nOirear, which may have applied to an old half-barony near Enniskillen.[3]