The Scottish surname MacWilliams, also found in Ireland,  is an anglicized form of the Gaelic name Mac Uilleim, a patronymic from of a Gaelicized form of William, with the redundant addition of English patronymic -s. It is said that the clan originate from William fitz Duncan, the son of Duncan II of Scotland, and his son Duncan Ban MacWilliam, who was killed at the battle of Man Garvia, in Morayshire in 1187. It is said that the MacWilliams were powerful claimants for the Scottish throne against King William the Lion (1165 - 1214), since all claimed descent from King Malcolm III of Scotland, 1057 - 1093. The MacWilliam's  lost the argument as most of their leaders were dead in battle by the year 1215.