Linehan, Lenaghan, Lenihan A Gaelic surname septs of which include: ó Léanacheain, meaning descendant of Léanacháin, diminuative of Léanach meaning ‘cloaked’. A sept of Roscommon. In 1890 Linehan was principally found in Cork, Lenaghan was principally found in Antrim, and Lenihan was principally found in Limerick. The estimated number of bearers for all variants was 4,660.