Βροῦτος, the name of a plebeian family of the Junia Gens, which traced its descent from the first consul, L. Junius Brutus. (Comp. Cic. Phil. 1.6, Brut. 4.) It was denied by many of the ancients that this family could be descended from the first consul, first, because the latter was a patrician, and secondly, because his race became extinct at his death, as he had only two sons, who were executed by his own orders. (Dionys. A. R. 5.18, comp. 6.70; Dion. Cass. 44.12; Plut. Brut. 1.) Posidonius, indeed, asserted that there was a third son, who was a child when his brothers were put to death, and that the plebeian family was descended from him; and he even pretended to discover a likeness in many of the Bruti to the statue of the first consul. (Plut. l.c.) But this tale about a third son is such an evident invention, to answer an objection that had been started by those who espoused the other side of the question, that it deserves no credence; and nothing was more natural than that the family should claim descent from such an illustrious ancestor, especially after the murder of Caesar, when M. Brutus was represented as the liberator of his country from tyranny, like his name-sake of old. It is, however, by no means impossible, that the family may have been descended from the first consul, even if we take for granted that he was a patrician, as we know that patricians sometimes passed over to the plebeians: while this descent becomes still more probable, if we accept Niebuhr's conjecture (Rom. Hist. i. p. 522, &c.), that the first consul was a plebeian, and that the consulship was, at its first institution, shared between the two orders.

The surname of Brutus is said to have been given to L. Junius, because he pretended idiocy in order to save himself from the last Tarquin, and the word is accordingly supposed to signify an "idiot." (Liv. 1.56; Dionys. A. R. 4.67, who translates it ἠλίθιος; Nonius, p. 77.) Festus, however, in a passage (s. v. Brutum) which is pointed out by Arnold (Rom. Hist. i. p. 104), tells us, that Brutus, in old Latin, was synonymous with Gravis; which, as Arnold remarks, would show a connexion with βάρυς. The word may, therefore, as a surname, have been originally much the same as Severus. This conjecture we think more probable than that of Niebuhr's, who supposes it to mean a "runaway slave," and connects it with the Brettii, "revolted slaves," whence the Brutii are supposed to have derived their name (Strab. vi. p.225; Diod. 16.15; Gel. 10.3): he further observes, that this name might easily have been applied by the Tarquins to Brutus as a term of reproach. (Rom. Hist. i. pp. 63, 98, 515.)