Δροῦσος, the name of a distinguished family of the Livia gens. It is said by Suetonius (Suet. Tib. 3), that the first Livius Drusus acquired the cognomen Drusus for himself and his descendants, by having slain in close combat one Drausus, a chieftain of the enemy. This Livius Drusus, he goes on to say, was propraetor in Gaul, and, according to one tradition, on his return to Rome, brought from his province the gold which had been paid to the Senones at the time when the Capitol was besieged. This account seems to be as little deserving of credit as the story that Camillus prevented the gold from being paid, or obliged it to be restored in the first instance.

Of the time when the first Livius Drusus flourished, nothing more precise is recorded than that M. Livius Drusus, who was tribune of the plebs with C. Gracchus in B. C. 122, was his abnepos. This word, which literally means grandson's grandson, may possibly mean indefinitely a more distant descendant, as atavus in Horace (Hor. Carm. 1.1) is used indefinitely for an ancestor.

Pighius (Annales, i. p. 416) conjectures, that the first Livius Drusus was a son of M. Livius Denter, who was consul in B. C. 302, and that Livius Denter, the son, acquired the agnomen of Drusus in the campaign against the Senones under Cornelius Dolabella, in B. C. 283. He thinks that the descendants of this Livius Denter Drusus assumed Drusus as a family cognomen in place of Denter. There is much probability in this conjecture, if the origin of the name given by Suetonius ne correct; for the Senones were so completely subdued by Dolabella and Domitius Calvinus (Appian, Gall. iv. fr. 11, ed. Schweigh.), that they seem to have been annihilated as an independent people, and we never afterwards read of them as being engaged in war against Rome. On this supposition, however, according to the ordinary duration of human life, M. Livius Drusus, the patronus senatus of B. C. 122, must have been, not the abnepos, but the ad nepos, or grandson's grandson's son, of the first Drusus, and hence Pighius (l.c.) proposes to read in Suetonius ad nepos in place of abnepos.

Suetonius (Suet. Tib. 2) mentions a Claudius Drusus, who erected in his own honour a statue with a diadem at Appii Forum, and endeavoured to get all Italy within his power by overrunning it with his clientelae. If we may judge from the position which this Claudius Drusus occupies in the text of Suetonius, he was not later than P. Claudius Pulcher, who was consul in B. C. 249. It is not easy to imagine any rational origin of the cognomen Drusus in the case of this early Claudius, which would be consistent with the account of the origin of the cognomen given by Suetonius in the case of the first Livius Drusus. The asserted origin from the chieftain Drausus may be, as Bayle (Dictionnaire, s. v. Drusus) surmises, one of those fables by which genealogists strive to increase the importance of families. The connexion of the family of Drusus with the first emperors probably reflected a retrospective lustre upon its republican greatness. (Verg. A. 6.825.)