McGuire (also spelled "Maguire") is a surname of Irish origin, from the Gaelic "Mag Uidhir". The name means "son of Odhar" Some historical background indicates the name Mag Uidhir, Maguire or McGuire stems from the Magi of Éire who were the priests of ancient Ireland. The name is most often associated with County Fermanagh. The McGuire Royal Family (Maguidhirs) lived in the McGuire (Maguidhir) castle in Enniskillen. The origins of the island town of Enniskillen go back to prehistory when this short nexus was the main highway between Ulster and Connaught. Enniskillen Castle was the medieval seat of the McGuire (Maguidhir), chieftains of Fermanagh, who policed the lough with a private navy of 1,500 boats. Nearby is Maguiresbridge. At the castle, the King heard wind of a large army that had been sent to attack. Fearing the loss of all his clan, he sent half of his people to the northwest of Scotland, who adopted the surname of MacQuarrie.
^Sources: 1) The Fermanagh Story by Peadar Livingstone, published 1969, Cumann Seanchais Chlochair; 2) Irish Families, Their Names, Arms, and Origins by Edward MacLysaght; 3) Historic Maguire Chalices by The Maguire of Fermanagh, published 1996 by Fermanagh District Council; 4) Irish Book of Arms plates; 5) Irish Chiefs and Leaders by Rev. Paul Walsh, published 1960, Dublin