late 14c., from Latin centaurus, from Greek Kentauros, origin disputed. In early Greek literature they were a savage, horse-riding tribe from Thessaly; later they were monsters half horse, half man. The southern constellation of Centaurus is attested in English from 1550s but was known by that name to the Romans and known as a centaur to the Greeks. It has often been confused since classical times with Sagittarius.