Mac Giolla Chaoin
Mac GIOLLA CHAOIN, Mac GIOLLA CHAOINE—IV—M'Gillekyne, M'Gillychyna, M'Gillechyny, Kilcoyne, Coyne; 'son of Giolla caoin' (the gentle youth) or 'son of Giolla Chaoine' (servant of St. Caoine, gentleness); apparently only different forms of the same surname which, in the 16th century, was found chiefly in Co. Leitrim and in the neighbourhood of Dublin. Mac Giolla Chaoine was probably the original, and Mac Giolla Chaoin an apocopated form. The same peculiarity, it will be noticed, attaches to Ó Maolchaoin and Ó Maol Chaoine, which see.
Alphabetical Index to Irish Surnames