catholicism - Who are called Catholics in the Early Church ... Catholicos, plural Catholicoi, is a title used for the head of certain churches in some Eastern Christian traditions. The title implies autocephaly and in some cases it is the title of the head of an autonomous church. The word comes from ancient Greek καθολικός, pl. καθολικοί, derived from καθ' ὅλου (kath'olou ...