Lewis & Short

2. Dīs, ītis (nom. Dītis, Petr. Poët. 120, 76; Quint. 1, 6, 34; cf. Serv. Verg. A. 6, 273; the nom. Dis very rare in the poets; Aus. Idyl. 12: de deis, 3), m. [cf.: dīus, divus, deus], orig. denoting godhead, deity, in general, and of Jupiter in partic.; cf.: Diespiter and Diovis = Juppiter; afterwards exclusively as the designation of the god of the infernal regions, the Greek Pluto, connected with pater, Varr. L. L. 5, § 66 Müll.; identified by Caesar with the Celtic god of night, cf. Caes. B. G. 6, 18, 1 sq.; Cic. N. D. 2, 26; Tac. H. 4, 84 fin.; Suet. Oth. 8; Inscr. Orell. 1465-1470 and 4967; without pater, Verg. G. 4, 519; id. A. 4, 702; 5, 731; 6, 127 al.: pallida Ditis aqua, Tib. 3, 1, 28: Ditis ignava aqua, id. 3, 3, 38; Ov. M. 4, 438; 511; id. F. 4, 449 al.: domina Ditis = Proserpina, Verg. A. 6, 397.