For a long time the city possessed a Thracian name, Serdica, derived from the tribe ''Serdi'', who were either of Thracian, Celtic, or mixed Thracian-Celtic origin. The emperor Marcus Ulpius Traianus (53–117 AD) gave the city the combinative name of ''Ulpia Serdica''; Ulpia may be derived from an Umbrian cognate of the Latin word ''lupus'', meaning "wolf" or from the Latin ''vulpes'' (fox).