faith (n.) Look up faith at Dictionary.com
mid-13c., "duty of fulfilling one's trust," from Old French feid, foi "faith, belief, trust, confidence, pledge," from Latin fides "trust, faith, confidence, reliance, credence, belief," from root of fidere "to trust," from PIE root *bheidh- (source also of Greek pistis; see bid). For sense evolution, see belief. Theological sense is from late 14c.; religions called faiths since c.1300.