A name deriving from the Gaelic Buth Chanain meaning 'house of the canon', it may have arisen through service to the old Celtic Church. Lands on the shores of Loch Lomond, including the small island of Clairinsh, were granted to Absalon, the progenitor of the family, by the Earl of Lennox in 1225. It is not clear whether the family took its name from the land, or gave its name to the land, but Absalon may have been a clergyman. Clairinsh (or Clarinch) became their war-cry. The lands were confirmed by the Earl of Lennox to a certain Maurice de Bouchannane in 1282, giving him the right to hold courts.
In 1421, Sir Alexander Buchanan fought alongside other Scottish nobles in the Battle of Beauge for the French against the English. It is said he killed the Duke of Clarence and took his cap as a trophy. Hence the ducal cap held high in the family crest.
Notable Buchanans include poet and royal tutor George Buchanan (1506-82); Glasgow tobacco merchants George Buchanan (1686 - 1773) and Andrew Buchanan (1690 - 1759), the son of the first, another Andrew, gave his name to Buchanan Street in the city; poet Dugald Buchanan (1716-63); explorer and naturalist Francis Hamilton Buchanan (1762 - 1829); the New Zealand naturalist John Buchanan (1819-98); actor Jack Buchanan (1891 - 1957) and the boxer Ken Buchanan (b.1945).