defyyoudaoicibaDictYouDict[defy 词源字典]
defy: [14] The underlying notion of defy is of the renunciation of allegiance. It comes via Old French defier from a Vulgar Latin *disfidāre ‘renounce one’s faith’, a compound verb formed from the prefix dis-, denoting reversal, and Latin fīdus ‘trusting’. This adjective came from a lengthened variant of the stem which produced fidēs ‘faith’, source of English faith.

The word’s current main sense represents a slight shift from ‘being disloyal’ to actively ‘challenging someone’s power’. The verb’s noun derivative defiance [14], borrowed from Old French, has a first cousin in diffidence [15], originally ‘distrustfulness’, which came from the classical Latin compound verb diffidere ‘mistrust’.
=> diffidence, faith[defy etymology, defy origin, 英语词源]
defy (v.)youdaoicibaDictYouDict
c. 1300, "to renounce one's allegiance;" mid-14c., "to challenge, defy," from Old French defier, desfier "to challenge, defy, provoke; renounce (a belief), repudiate (a vow, etc.)," from Vulgar Latin *disfidare "renounce one's faith," from Latin dis- "away" (see dis-) + fidus "faithful," from the same root as fides "faith" (see faith).