Buchanan
Buchanan—This Scottish name in Ulster and Scotland is known by the name of M'Whannan and Mewhannan in many parts of the two countries, from the ancient name of the district of Buchanan in Stirling County, Scotland, which was Mac A'Chanonaich. The ancient clan name was McAuslan, the name being derived from Ausalan Buoy O'Kayn (O'Kane), the founder of the clan in the 11th century, a chief of a branch of the O'Kanes of Co. Derry. In the 13th century Gilbrid Mac Auslan, of the junior branch of the clan, assumed the territorial name of Buchanan, dropping the surname Mac Auslan, and from him descended a family in Co. Tyrone, one of whose descendants was James Buchanan, President of the United States of America. The senior branch of the clan still retain the ancient name of MacAuslan, from whom some families of McCausland settled in the 17th century in Co. Derry. In Gaelic, Mac Ausaláin. Other anglicised forms are McCaslan, in Co. Armagh, and McAuslin and McCasland in various parts of Ulster.