Drusus (cognomen)
Drusus was a cognomen in Ancient Rome originating with the Livii. Under the Republic, it was associated with the Livii Drusi. Under the empire and owing to the influence of the empress Livia, the name was used by several members of the Julio-Claudian dynasty. During that period, when a line reached two or three branches calling for four or five names, the Romans shortened to one or two; consequently, "Drusus" could seem to be used in place of a praenomen. True praenomina, however, could be assigned to anyone within the customary usage of their clan, but Drusus could only be used in lines that had it as an agnomen.
