Cahan

The O'Cahans (Irish Uí Chatháin, descendants of Cahan) were a powerful sept of the Cenél nEógain of mid-Ulster. They originated in Laggan in eastern Donegal and moved east in the twelfth century, ousting the O'Connors from Keenaght; their lordship of Keenaght and Coleraine became known as O'Cahan's country. The sept first appears on record in 1138.

As vassals of their kinsmen the O'Neills, they inaugurated each new O'Neill chief by casting a shoe over his head. Fifteen O'Cahan chieftains fell fighting the Normans at Drumderg.

Most chiefs fled in the Flight of the Earls in 1607; Donnell Ballagh O'Cahan was captured and died in the Tower of London in 1626, and the lordship was absorbed into the Plantation of Ulster. The harpist Rory Dall O'Cahan may have composed the Londonderry Air as a lament for the fallen sept.