The term Gallowglass or Galloglass is an Anglicisation of the Irish, Gallóglaigh ("foreign soldiers"), incorporating the Celtic word Óglach, which is derived from oac, the Old Irish for "youths", but later meaning "soldier". warrior.]] Encarta specifies the plural of Gallowglass to be 'Gallowglasses', but this article assumes that the singular and plural terms are both 'Gallowglass'. Shakespeare uses the form "gallowglasses" in the play Macbeth. The gallowglass were a mercenary warrior élite among Gaelic-Norse clans residing in the Western Isles of Scotland (or, Hebrides) and Scottish Highlands from the mid 13th century to the end of the 16th century. As Scots, they were Gaels and shared a common origin and heritage with the Irish, but as they had intermarried with the 10th century Norse settlers of the islands and coastal areas of Scotland and the Picts, the Irish called them Gall Gaeil (