According to Janet and Colin Bord,

… there are  numerous examples of river names which contain or were derived from Celtic deity names … The Clyde comes from Clota, the ‘Divine Washer’. (Scottish tales of a hag washing the bloody clothes of those shortly to die, called ‘The Washer at the Ford’, may be a memory of this goddess.)

Janet and Colin Bord, Sacred waters, Paladin 1985, p14