ferocious: [17] Etymologically, ferocious means ‘wild-eyed’. It comes from Latin ferox, which was originally a compound formed from ferus ‘fierce, wild’ (source of English feral [17]) and an element -oc-, -ox meaning ‘looking, appearing’. This also appears in atrocious and ocular, and goes back to an Indo-European source which also produced Greek ōps ‘eye’ and English eye. => atrocious, eye, feral, ocular
1640s, from Latin ferocis, oblique case of ferox "fierce, wild-looking" (see ferocity). Alternative ferocient (1650s) is seldom seen. Related: Ferociously; ferociousness.
