Origin: 1300–50; ME < MF afiance, equiv. to afi(er) to pledge faith, declare on oath, betroth (< ML affīdāre, equiv. to ad-ad-+ *fīdāre, for L fīdere to trust; see confide) + -ance-ance
af·fi·ance (ə-fī'əns) tr.v.
af·fi·anced, af·fi·anc·ing, af·fi·anc·es To bind in a pledge of marriage; betroth.
[From Middle English affiaunce, assurance, from Old French, from affier, to trust to, from Medieval Latin affīdāre : Latin ad-, ad- + Latin fīdus, faithful; see bheidh- in Indo-European roots.]