Ó Cillín
Ó CILLÍN—I—O Killine, O Killen, Killeen, Killen, Killian, Killion; 'descendant of Cillín' (a 'pet' diminutive of Ceallach, war); the name of several distinct families in different parts of the country, as Clare, Galway, Mayo, Westmeath, Offaly, Kildare and Down, in all of which it is still extant.
Alphabetical Index to Irish Surnames