Ó Giolláin
Ó GIOLLÁIN—I—O Gillane, O Gillain, Gillane, Gillan, Gilland, Gillon, Gillen; 'descendant of Giollán' (diminutive of giolla, servant, youth); the name of a family of Cinel Eoghain; given by MacFirbis as an alias for Ó Giollagáin, which see.
Alphabetical Index to Irish Surnames