The Scottish surname McKewen is an anglicized form of Gaelic Mac Eoghain ‘son of Eoghan’, a widespread and ancient personal name. The principal Scottish clan with the name MacEwen / McEwen was Clan MacEwen of Otter that was centred on the shores of Loch Fyne in Argyll. They claim descent from Anrothan O'Neill, who left Ireland for Kintyre in the 11th century. They can claim a further descent from the legendary Niall Noigíallach, High King of Ireland, who lived from the mid 4th century to early 5th century. In the 15th century the MacEwens of Otter lost their lands to the Campbells, and since then the line of chiefs has been untraced. A notable bearer of the name was John "Black Jack" McEwen the famous politician and the 18th Prime Minister of Australia.