MacGuire, Maguire, Mag Uidhir, A Gaelic surname meaning son of Odhar genative of uidhir dun coloured perhaps the early name of the otter used as a personal name, also anglicised as Maguire and MacGuire. The leading sept of Fermanagh from the thirteenth century. They were dispossessed at the time of the Plantation of Ulster. In 1890 Maguire was the most numerous surname in Fermanagh, it was the thirty-ninth most numerous surname in Ireland, and the estimated number of bearers was 14,400. The surname was principally to be found in Fermanagh, Dublin, Cavan and Donegal and it was found as McGuire in Roscommon and Mayo. In the United States Maguire is the 2,407th most numerous surname with an estimated 13,750 bearers, and it is numerous in the state of Massachusetts.