Is it ensure, insure, or assure?
early 14c., "Lady Day," from Anglo-French anunciacioun, Old French anonciacion, from Latin annuntiationem (nominative annuntiatio), noun of action from past participle stem of annuntiare (see announce). The Church festival (March 25) commemorating the visit of the angel Gabriel to the Virgin Mary, foretelling the incarnation. General sense of "an announcing" is from 1560s. Old English for "Annunciation Day" was bodungdæg.