Padraig Mac Giolla-Domhnaigh

Douglas—This name, according to William Buchanan, was early written MacDouglas, and the sept is descended from McDuff, Thanes of Fife, Scotland, and the origin of the name arose from the black complexion and grey green dress of the first owner of the name, dubh—black, and glas—grey-green, (Mac Dubhglas).

Alphabetical Index of Anglicised Surnames in Ireland

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