Nickname, of Celtic origin, meaning "foreigner" or "stranger". In the Scottish Highlands the Gaelic term gall was applied to people from the English-speaking lowlands and to Scandinavians; in Ireland the same term was applied to settlers who arrived from Wales and England in the wake of the Anglo-Norman invasion of the 12th century. The surname is also found at an early date in Lincolnshire, where it apparently has a Breton origin, having been introduced by Breton followers of the Norman Conquerors.