About the middle of the thirteenth century, Gilbert, seneschal to the Earl of Lennox obtained from him a part of the lands of Buchanan in Stirlingshire and took his name from them. An ecclesiastical origin is claimed for the surname, as in Gaelic a Buchanan is know as Mac-a' Chanonaich, or the Son of Canon--and the place-name Buchanan (Both-chanain) really means the canon's seat.
Donald, 6th Earl of Lennox, renewed to maurice of Buchanan the grant conferred by a former Earl on his ancestor, and the King granted a charter of confirmation to his successor of the same name.
Through marriage with the daughter of Menteith of Ruskie, his son, Walter of Buchanan, became connected with the Royal House. The latter married the sole heiress of the ancient family of Leny. Their eldest son, Sir Alexander, distinguished himself as a soldier, and was slain in the battle of verneuil in 1424. His second brother, Walter, succeeded to Buchanan, and his third to Leny.
Walter married Isabel, Countess of lennox. Their eldest son, Patrick, married the heiress of Killearn and Auchreoch. Patrick's son, Walter, married a daughter of Lord Graham. Patrick , who fell at Flodden, by his wife, a daughter of Argyll, left two sons- George, Sheriff of Dunbarton in 1561, and Walter, the founder of the House of Spittal.
By Margaret Edmondson of Duntreath, he had a son John, his heir, and by his second wife, Janet Cunninghame of Craigends, William, founder of the now extenct line of Auchmar.
The principal line became extinct early in the eighteenth century; and though in 1878 Francis hamilton Buchanan of Leny established his claim as chief, his grandson, J.H. Buchanan of Leny, died in 1919 without issue. Since then the chiefship has been dormant.
The Buchanan family lands are now possessed by the Duke of Montrose. There is a Buchanan Society in Glascow, which holds Clar-inch, the island in Loch Lomond from which the slogan is derived.
