onychius Save Lewis & Short DMLBS ŏnychĭus, a, um, adj. [onyx], of or belonging to onyx: onychius lapis, i. e. onyx, Tert. adv. Marc. 2, 10. onychius [ML; cf. LL onychium < ὀνύχιον] , of onyx, onyx-; (~ius lapis) onyx stone. onichius lapis Bacon CSPhil. 443.