early 15c., "assertion that something is true," from Old French afermacion (14c.), from Latin affirmationem (nominative affirmatio) "an affirmation, solid assurance," noun of action from past participle stem of affirmare (see affirm). In law, as the Quaker alternative to oath-taking, it is attested from 1690s.[affirmation etymology, affirmation origin, 英语词源]