Meaning

verb to declare or affirm solemnly and formally as true

verb admit openly and bluntly; make no bones about

originFrom Middle English avowen, from Old French avouer, from Latin advocare (“to call to, call upon, hence to call as a witness, defender, patron, or advocate”), from ad (“to”) + vocare (“to call”). Doublet of advoke, avouch, and advocate. Not related to vow.

Etymology from Wiktionary, CC BY-SA 3.0