c.1600, from French férocité, from Latin ferocitatem (nominative ferocitas) "fierceness," from ferocis, oblique case of ferox "bold, courageous, warlike; fierce, savage, headstrong, cruel," literally "wild-looking," a derivative of ferus "wild" (see fierce) + -ox, -ocem (genitive -ocis), a suffix meaning "looking or appearing" (cognate with Greek ops "eye, sight;" see eye, n.).