Copyright The Columbia University PressThe Columbia Encyclopedia, 6th ed. The Columbia University Press
Dermot McMurrough or Diarmiud mac Murchada (both: dûr´mət məkmŭr´ə), 1110–71, Irish king of Leinster. He became involved in a complicated feud, partly because he abducted a neighbor's wife, and in 1166 was defeated and banished by the High King Rory O'Connor. Dermot appealed for help to Henry II of England, who refused him direct support but allowed him to enlist a force led by Richard de Clare, 2d earl of Pembroke, and other Norman barons in Wales. After Pembroke had invaded (1170) and won much of E Ireland, including Dublin, he married Dermot's daughter, Eva. He was a patron of the compilation of the valuable Irish manuscript, the Book of Leinster.