Meaning

verb report or maintain

verb to declare or affirm solemnly and formally as true

originFrom Middle English aver, avere (“workhorse; any beast of burden (?); things which are owned, possessions, property, wealth; state of being rich, wealth; ownership, possession”) [and other forms], and then either: * from Old French aver, aveir, avoir (“possession, property; (collectively) beasts of burden; domestic animals; cattle”) (modern French avoir (“asset, possession”)), from aveir, avoir…

Etymology from Wiktionary, CC BY-SA 3.0