Aver

глагол 1) утверждать, заявлять Например: He averred that he was innocent. — Он утверждал, что невиновен. Синоним(ы): assert 2) [юриспруденция] доказывать

Большой англо-русский словарь

Aver

transitive verb (averred; averring) Etymology: Middle English averren, from Anglo-French averer, from Medieval Latin adverare to confirm as authentic, from Latin ad- + verus true — more at very 1. a. to verify or prove to be true in pleading a cause b. to allege or assert in pleading 2. to declare positively

Merriam-Webster's Collegiate Dictionary