Carr
Carr—This name in Southern parts of Donegal, especially the original location of the sept, and in other parts of the Northwestern counties of Ulster is the anglicised form of McElhar and McIlhair (Mac Giolla-Chatair). It is also changed to Kerr, to my own personal knowledge in the latter case in Armagh and Tyrone.
Alphabetical Index of Anglicised Surnames in Ireland
See also Woulfe’s Irish Names and Surnames
… and O'Hart's Irish Pedigrees