The following family names are derived from the Gaelic-Mac Suibhne, Sweeny; Sweeney; Swain; Swayne; Swyney; Swyny; Swiney; Sweney; Swiggan; MacSweeney; MacSwiney; and MacSwiggan.

    The Sweeny family is descended from Milesius, King of Spain, through the line of his son Heremon. The founder of the family was Eogan ancestor of the Northern Hy Nials, and son of Nial of the Nine Hostages. The ancient name of the McSweeneys was Suibne O'Donnell the first part of which refers to "Arms" and the second to "Destroyer". The name Sweeney was taken from Suibne Mean ("Renowned"), monarch of Ireland, A. D. 628. The chiefs of this sept bore the title of Lords of Tuatha, and their possessions were located in Donegal and Cork.   

    The McSweeneys were a branch of the O'Neills, and settled in Tir-connell (Donegal) at an early period, where they branched into three great families. These were, 1. The McSuineys of Fanaid, who possessed an extensive territory west of Lough Swilly, and whose castle was at Rathmullin. 2. The McSweeny Boghamach, or of Boghani, now the barony of Banagh, and whose castle was at Rathain, and which territory, included Reachrain Muintiri Birn, now Rathlin O'Bierne Islands. 3. The MacSweeney Na d-Tuath, or the McSwcency of the Battle Axes. These chiefs were so named because they were standard bearen of the O*Donnells, and chiefs of the Gallowglasses—the heavy-armed Irish infantry of those days. A branch of this family settled in County Cork, in the thirteenth century, where they became commanders, under the MacCarthys, Princes of Desmond.