Well, Taurus and Tauros certainly are the ancient Latin and Greek names of the constellation, but Taurean as a given name probably has a more recent origin. As a modern given name, it seems to have been created as the stage name of the actor Taurean Blacque, who at birth was named
Herbert Middleton Jr. His most famous role was as detective
Neal Washington on the 1980s American television series
Hill Street Blues. If your friend was born after 1981 in the USA, or even close enough to the Canal Zone in Panama to be exposed to American television, his parents were probably inspired by Mr. Blacque's fame.
http://www.imdb.com/name/nm0086000/