Clan Buchanan is an Armigerous

Armigerous clan

An armigerous clan is a Scottish clan, family or name which is registered with the Court of the Lord Lyon and once had a chief who bore undifferenced arms, but does not have a chief currently recognized as such by Lyon Court...

 Scottish clan

Scottish clan

Scottish clans , give a sense of identity and shared descent to people in Scotland and to their relations throughout the world, with a formal structure of Clan Chiefs recognised by the court of the Lord Lyon, King of Arms which acts as an authority concerning matters of heraldry and Coat of Arms...

 whose origins are said to lie in the 1225 grant of lands on the eastern shore of Loch Lomond

Loch Lomond

Loch Lomond is a freshwater Scottish loch, lying on the Highland Boundary Fault. It is the largest lake in Great Britain by surface area. The lake contains many islands, including Inchmurrin, the largest fresh-water island in the British Isles, although the lake itself is smaller than many Irish...

 to clergyman Sir Absalon of Buchanan by the Earl of Lennox

Earl of Lennox

The Mormaer of Lennox or Earl of Lennox was the ruler of the long-lasting provincial Mormaerdom/Earldom of Lennox in the Medieval Kingdom of the Scots. The first Mormaer is usually regarded as Ailin I , but the genealogy of the Mormaers gives earlier names...

.
Traditionally, Clan Buchanan can trace its origin back to Anselan O Kyan

Anselan O Kyan

Anselan O Kyan, who was a son of one of the kings of Ulster, landed on the northern coast of Argyl, near the Lennox, about the year 1016. Assisting Malcolm II of Scotland in repelling his old enemies the Danes, on two different occasions. Upon their arrival in Scotland, he received a grant of land...

 who was a son of the King of Ulster who landed in Argyll in 1016. For his services against the Danes he received the lands of Buchanan, which lie to the east of Loch Lomond

Loch Lomond

Loch Lomond is a freshwater Scottish loch, lying on the Highland Boundary Fault. It is the largest lake in Great Britain by surface area. The lake contains many islands, including Inchmurrin, the largest fresh-water island in the British Isles, although the lake itself is smaller than many Irish...

 around the village of Killearn

Killearn

Killearn is a small village of approximately 1700 people in the Stirling council area of Scotland. The village name stems from the Gaelic Cill Earnain, meaning Ernan's Church; the Ernan in question presumably being one of the canonised individuals of that name who were both relatives and followers...

.

Clan Buchanan has occupied the lands surrounding the shores of Loch Lomond

Loch Lomond

Loch Lomond is a freshwater Scottish loch, lying on the Highland Boundary Fault. It is the largest lake in Great Britain by surface area. The lake contains many islands, including Inchmurrin, the largest fresh-water island in the British Isles, although the lake itself is smaller than many Irish...

 since 1225 as a result of a grant by the Earl of Lennox

Earl of Lennox

The Mormaer of Lennox or Earl of Lennox was the ruler of the long-lasting provincial Mormaerdom/Earldom of Lennox in the Medieval Kingdom of the Scots. The first Mormaer is usually regarded as Ailin I , but the genealogy of the Mormaers gives earlier names...

 to Sir Absalon of Buchanan in which he is referred to as 'clericus meus', meaning 'my clergyman'.