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
