Drusus was a cognomen in Ancient Rome originating with the Livii. Under the Republic, it was the intellectual property and diagnostic of the Livii Drusi. Under the empire and owing to the influence of an empress, Livia Drusilla, the name was used for a branch of the Claudii into which she had married: the Claudii Drusi. 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.
Male members of the Livii Drusi, a branch of the Livia gens:
Gaius Livius Drusus, consul in 147 BC
Marcus Livius Drusus, the name of two Republican politicians:
Marcus Livius Drusus (consul) (died 108 BC), father
Marcus Livius Drusus (tribune) (died 91 BC), son
Marcus Livius Drusus Claudianus (died 42 BC), adopted from the Claudii (hence Claudianus) by the tribune and the father of Livia Drusilla, Augustus' third wife
Marcus Livius Drusus Libo (born 1st-century BC), adopted by Claudianus from the Scribonii Libones (hence Libo), consul in 15 BC
Male members of other clans whose mother belonged to the Livii Drusi and had given her son the agnomen Drusus in commemoration of that fact, even though he was not by law of the Livii Drusi. The most noted example is perhaps the Claudii Drusi, who were given the name Drusi by their mother Livia Drusilla. They were not Livii Drusi, but a new branch of the Claudii.
Drusus Claudius Nero I, grandfather of Tiberius.
Nero Claudius Drusus Germanicus, the brother of Tiberius. Also called Drusus I. Was born Decimus Claudius Drusus before his name was changed to Nero Claudius Drusus.
Nero Claudius Drusus, possible birth name of Germanicus, son of Nero Claudius Drusus. Possibly called Tiberius Claudius Nero, later called either Nero Claudius Drusus Germanicus or Tiberius Claudius Nero Germanicus, later called Germanicus Julius Caesar.
Tiberius Claudius Drusus, the birth name of emperor Claudius, later known as Tiberius Claudius Nero Germanicus and Tiberius Claudius Caesar Augustus Germanicus. He was the son of Nero Claudius Drusus.
Drusus Julius Caesar (13 BC–23 AD), son of Tiberius. Also called Drusus II or Drusus Minor. Was born Nero Claudius Drusus.
Marcus Scribonius Libo Drusus, a great-grandson of Pompey who in AD 16 was charged with plotting against Tiberius, Germanicus, and Drusus Julius Caesar
Drusus Julius Caesar Germanicus (7–33 AD), son of Germanicus. Also called Drusus III.
Tiberius Claudius Drusus (16-20 AD), son of Claudius.
Nero Claudius Caesar Drusus Germanicus (37–68 AD), adoptive name of emperor Nero. Previously known as Lucius Domitius Ahenobarbus and later known as Nero Claudius Caesar Augustus Germanicus.
Drusus Claudius Nero, the name of two prominent Roman citizens
