Lewis & Short

Sūtrĭum, ii, n., an ancient town in Etruria, now Sutri, Liv. 6, 3, 2; 6, 9; 6, 32; Vell. 1, 14.
Prov.: quasi eant Sutrium, i. e. to set about any thing well prepared (as Camillus, when he marched to the conquest of Sutrium), Plaut. Cas. 3, 1, 10; cf. Fest. p. 310 Müll.
Hence,

  1. A. Sūtrīnus, a, um, adj., of or belonging to Sutrium: ager, Liv. 26, 34: colonia, Plin. 3, 5, 8, § 51.
    Subst.: Sūtrīni, ōrum, m., the inhabitants of Sutrium, Liv. 6, 3.
  2. B. Sūtrĭus, a, um, adj., of Sutrium: tecta, Sil. 8, 493.