1. To admit openly and bluntly: "She avowed that she was innocent of the accusations."
2. To declare or to affirm solemnly and formally as true: "At the end of most wedding ceremonies, the couples make their vows, in which they avow their commitment to each other."
3. To acknowledge openly, boldly, and unashamedly.

To confess, or "to avow guilt" does NOT come from the same Latin source as vow (from Anglo-French and Old French vou) which comes from Latin votum, "a vow, a wish, a promise, a dedication".

Avow comes from Latin, vocare, "to call". From Old French avouer, "acknowledge, accept"; especially, as a protector, from Latin advocare.