What is "mathghamhain"

Mathghamhain (also spelled Mathgamain or Mathúin and anglicised Mahon) was an Irishman of the early 11th century. He was the son of Cian Mac Mael Muda, chief of the Cineal Aodha, and his wife Sadhbh, who was daughter of the High King Brian Boru. Through Brian Boru, Mathghamhain was a member of the Eoghanacht Raithline, a dynastic line claiming descent from Eoghan Mor, a 2nd-century King of Munster. Mathghamhain (whose name means bear) was killed at the Battle of Clontarf in 1014.

Mathghamhain's descendants eventually became sovereigns over territory in west Cork, notably around the Iveagh Peninsula and the town of Bandon. Today, his descendants use the surname McMahon, Mahoney, O'Mahoney, Mahony, Mahaney or O'Mahony.