CAHER (Cahir), market town in a good agricultural district, Co. Tipperary, Ireland, at the foot of the east end of the Galtee mountains on the river Suir, midway between Clonmel and Tipperary on the Gt. Southern Railway. Pop. (1926) 1,707. An ancient fortress on an island in the river was called Dun-iasgach (Fortress abounding in fish). Caher derives from Cathair, a stone fortress. The present castle was built (1142) by O'Connor, earl of Thomond. Ardfinnan castle (Norman) stands 6 m. down the Suir; there are stalactite caverns at Mitchelstown to m. southwest.