Ó Cartáin
Ó CARTÁIN—I or IV—O Cartaine, O Cartayne, O Cartan, Cartan, Carton, Carten, Cartin, Curtan, Curtayne, Curtin, &c.; 'descendant of Cartán,' if not a corruption of Mac Artáin (which see), which seems probable. At the beginning of the 17th century, it was found chiefly in the midlands—Westmeath and Longford—but appears also at Castleisland, Co. Kerry, where it is now pronounced Ó Curtáin, and anglicised Curtin, &c, as it is also in West Limerick where it is now very common. See Mac Cairteáin.
Alphabetical Index to Irish Surnames