1. cassis, ĭdis (access. form cassĭda, ae, like chlamyda from chlamys, Prop. 3 (4), 11, 15; Verg. A. 11, 775; cf. Prob. II. p. 1473 P. Lind.; Charis. p. 80 P.; Prisc. p. 698 ib. Also Paul. ex Fest. p. 48, instead of cassilam, the reading should be cassidam), f. [Etruscan, acc. to Isid. Orig. 18, 14, 1; cf. Müll. Etrusk. 1, p. 392; cf. Sanscr. khad, to cover, and Lat. castrum, casa], a helmet, commonly of metal (as galea was of leather, Isid. Orig. 18, 14, 1; cf. Tac. G. 6), Plaut. Trin. 3, 2, 100; Caes. B. G. 7, 45; Ov. M. 12, 89; 13, 107: fracta, Juv. 10, 134: caelata, id. 11, 103.
But also promiscuously for galea, Ov. M. 8, 25 (cf.: aerea galea, Verg. A. 5, 490).