Origen: Irlandés. Encontrados primero en el condado de Fermanagh. Irish surnames are all based on the Gaelic language native to Ireland. The original Gaelic form of the name McCusker is Mag Uidhir, which is derived from the word odhar, meaning dun-colored; in the genitive case, the word is uidhir.

Variantes: MacCosker, MacCusker, MacOsker, MacOscar y otros.