affiance (v.) Look up affiance at Dictionary.com
1520s, "to promise," from Old French afiancier "to pledge, promise, give one's word," from afiance (n.) "confidence, trust," from afier "to trust," from Late Latin affidare, from ad- "to" (see ad-) + fidare "to trust," from fidus (see affidavit). From mid-16c. especially "to promise in marriage." Related: Affianced; affiancing.