The Buchanan Clan is thought to have originated in 1016 A.D. when Anselan O’kyan (or Absalon) fled Ireland. He was the son of the reigning Ulster monarch and was forced to flee Ireland by Canute the Dane. He was then employed by Malcom II, the Scottish King, to defend against Norse attacks in the west. He was awarded land, through the marriage into the family of the Earl of Lennox on the east bank of Loch Lomond. The Buchanan lands lying to the east of the Loch Lomond remained in the clan for nearly seven centuries. The lands and the Bucahan House were sold in 1682 to the 3rd Marquess of Montrose on the death of John, the 22nd laird. Despite the number of cadet branches, the clan dispersed.

The Buchanan Clan has one of the oldest established clan societies in Scotland, which owns the clan’s most prized possession, its heartland from which it gets its warcry. This small island, measuring just half a mile in length, named Clar Innis or Clarinch, on Loch Lomond. It is on this island that the clan was first recorded in 1225. That was when the island was given to Sir Anselan of Absalon of Buchanan, said to be the son of Macbeth.