- faith
- mid-13c., "duty of fulfilling one's trust," from O.Fr. feid, from L. fides "trust, belief," from root of fidere "to trust," from PIE base *bhidh-/*bhoidh- (cf. Gk. pistis; see bid). For sense evolution, see belief. Theological sense is from late 14c.; religions called faiths since c.1300. Old Faithful geyser named 1870 by explorer Gen. H.D. Washburn, Surveyor-General of the Montana Territory, in reference to the regularity of its outbursts.