Padraig Mac Giolla-Domhnaigh

Williamson—This name is of Scottish origin, anglicised from M'William. The name belongs to a sept of the M'Farlanes as also belongs the Williams and M'Killiams in Aberdeen County. The name is rendered M'Quilliams in Galloway and N.E. Ulster, and Quilliam in the Isle of Man (which see).

Alphabetical Index of Anglicised Surnames in Ireland

See also Woulfe’s Irish Names and Surnames
and O'Hart's Irish Pedigrees