Last name: Cass. This interesting surname recorded as Cass, Cassie, Cassey and Cassy, is of the group of surnames which derive from medieval female personal names. Cass or Cassie is a pet-form of the popular female given name Cassandra, a Greek name meaning snarer of men, and introduced into Britain about the time of the famous crusades. This was the name of an ill-fated Trojan prophetess of classical legend, who was condemmed to foretell the future but never to be believed!