or TRISTLE DERMOY, an ancient town of Ireland, county of Kildare, on the river Lerr, 6 miles N. by E. of Carlow, and 53 from Dublin. An abbey was founded here by St Diarmid in 550. Among its antiquities are the remains of a large cathedral, part of which is now used as a parish church; a Franciscan monastery; a priory; a castle; a strong square tower; several crosses; and other ancient remains. It was the residence of the Dermots, kings of Leinster. Pop. (1841) 1416; (1851) 666.