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).