ferocious (adj.) Look up ferocious at Dictionary.com
1640s, from Latin ferocis, oblique case of ferox "fierce, wild-looking," from ferus "wild" (from PIE root *ghwer- "wild beast") + -ox (genitive -ocis), a suffix meaning "looking or appearing" (cognate with Greek ops "eye, sight;" from PIE root *okw- "to see"). Alternative ferocient (1650s) is seldom seen. Related: Ferociously; ferociousness.