De Cathair
de CATHAIR—XI—de Cathyr, de Cather, de Caher, Carr; Norman 'de Cathyr,' i.e., of Cahir, an Irish place-name, found very frequently all over the country; the name of an old Co. Limerick family of which we have record since the last quarter of the 13th century and which, though never numerous, is still extant in the county.
Alphabetical Index to Irish Surnames