What is "ahenobarbus"

Ahenobarbus was a cognomen used by a plebeian branch of the gens Domitia in the late Roman Republic and early Empire. The name means "red-beard" (literally, "bronze-beard") in Latin. According to legend, Castor and Pollux announced to one of their ancestors the victory of the Romans over the Latins at the battle of Lake Regillus, and, to confirm the truth of what they had just said, they stroked his black hair and beard, which immediately became red.