Lewis & Short

Brennus, i, m., = Βρέννος,

  1. I. a leader of the Gauls who defeated the Romans at the river Allia, Liv. 5, 38, 3; Serv. ad Verg. A. 6, 826.
    Hence, Brennĭcus, a, um, adj., of Brennus: signa, Sid. Carm. 7, 561.
  2. II. A king of the Gauls who invaded Greece in the second century B.C. and attacked Delphi, Cic. Div. 1, 37, 81; Just. 24, 5 sqq.; Val. Max. 1, 1, 18; Prop. 3, 13 (4, 12), 51.