the Owly" and "Bay of the Owles." Other English names were the Bay of Borace, Horrus, and Baragh, all references to Burrishoole (Buiríos Umhaill). The name 'Clew Bay', of uncertain origin, first appears in a 1714 map; it may be derived from cliath, "hurdle".

Clew Bay was the heart of the Gaelic territory of Umhaill, ruled by the Uí Máille (O'Malleys).