early 15c., "speak vainly or proudly," from Anglo-French vaunter, Old French vanter "to praise, speak highly of," from Medieval Latin vanitare "to boast," frequentative of Latin vanare "to utter empty words," from vanus "idle, empty" (see vain). Also short for avaunten "to boast" (see vaunt, n.). Related: Vaunted; vaunting.

"boasting utterance," c.1400, short for avaunt "a boast" (late 14c.), from avaunten "to boast" (c.1300), from Old French avanter "boast about, boast of, glory in."