Duff

Scottish and Irish: reduced Anglicized form of Gaelic Ó Duibh (‘descendant of Dubh’), Mac Giolla Duibh (‘son of the servant of Dubh’), or a short form of Duffin 2 (County Wexford), MacElduff (County Tyrone; see Kilduff), Mac Duibh, and Duffy, all of which are formed from personal names containing the element dubh ‘dark’, ‘black’ (widely used as a nickname or byname for a dark-haired man or man of dark temperament and as an element of personal names).