MacClenaghan with variations (e.g. MacClenahan), is about twice as numerous as MacLenaghan, which also has variants. Both are anglicized forms of Mac Leannacháin. It belongs almost exclusively to Ulster, especially Counties Antrim and Derry. It appeared in the Elizabethan Fiants in the O'Neill country and once among the Co. Cork "pardons" of 1601. Two testators of 1783, Mac Clenahan and Mac Clenachan, lived in or close beside north Tyrone. In 1878 de Burgh's Landowners shows that at that time both MacClenahans and MacLenahans held considerable estates in other Ulster counties. MacLennan may sometimes be a form of MacLenahan, though normally this is either the well known Scottish surname or a rare variant of MacAlhnion . MacLenahan is distinct from O'Lenahan.