Weir
Weir—This name is the anglicised form of one or two Irish and Scottish sept names. It is in the first case the anglicised form of Menair, and M'Nair, an Argyleshire sept ; written in Gaelic Mac An Mhaoir, the "Son of the Stewart or Keeper," the same form of the Co. Armagh sept who were Keepers of the Book of Armagh at Ballymoyer (Baile A' Mhaoir), the town of the Keeper; pronounced Ballywyre by the local people. In the second place it is the anglicised form of the Co. Cavan sept name of Corra-Curry (O'Corra) in the districts about Delvin and on parts of the borders of Cavan and Longford; also rendered Wyre and Wire in these localities, the word Córa, it is presumed, entering into the construction of the name.
Alphabetical Index of Anglicised Surnames in Ireland
See also Woulfe’s Irish Names and Surnames
… and O'Hart's Irish Pedigrees