Lewis & Short

Ăteste, is, n., = Ἀτεστέ (Ptol.), a town in the country of the Venetians, Plin. 3, 19, 23, § 130; 17, 17, 26, § 122; Tac. H. 3, 6; later called Ad Este and Ab Este, whence arose the present name, Este; cf. Mann. Ital. I. p. 97.
Hence, Ătestīnus, a, um, adj., of Ateste, Mart. 10, 93: ATESTINI, ōrum, m., the inhabitants of Ateste, Inscr. Orell. 3110.