The name may be derived from two elements in Irish: the first, os, means "deer"; the second element, cara, means "friend". The name is borne by a character in Irish mythology—Oscar, grandson of Fionn Mac Cumhail. The name was popularised in the 18th century by James Macpherson, creator of 'Ossianic poetry'. Today the name is associated with Scandinavia because Napoleon was an admirer of Macpherson's work and gave the name to his godson, Joseph Bernadotte, who later became Oscar I, King of Sweden. Consequently, at the time many Swedes were named Oscar. The name was given to more than a half-dozen members of Scandinavian royal houses.
The surname McCusker originates as an Anglicised form of the Irish Mac Oscair. The latter surname may originate from Oscar, or else from a Gaelicised form of the Old NorseÁsgeirr (a personal name itself composed of the elements meaning "god" and "spear").