Lewis & Short

Helvētĭi, ōrum, m.,

  1. I. the Helvetians, a people of Gallia Lugdunensis, in modern Switzerland, Caes. B. G. 1, 1; 4 sq.; Tac. G. 28; id. H. 1, 67; Plin. 4, 17, 31, § 106; Cic. Prov. Cons. 13, 33; id. Balb. 14, 32 et saep.
  2. II. Derivv.
    1. A. Helvētĭus, a, um, adj., of or belonging to the Helvetians, Helvetian: ager, Caes. B. G. 1, 2: civitas, id. ib. 1, 12.
    2. B. Helvētĭcus, a, um, adj., the same: proelium, Caes. B. G. 7, 9, 6.