aver

Etymology 1

From Middle English averren, from Old French averer, from Early Medieval Latin advērāre, a verb derived from Latin vērus (“true”). Compare Modern French avérer.

verb

1. (transitive, intransitive) To assert the truth of (something); to affirm (something) with confidence; to declare (something) in a positive manner.
   Now as to the Scriptures being the Word of God, and evidently known to be ſo, or evidencing themſelves to be ſo, and that of right, and properly they are to be ſo called; all which thou J. O. very abſolutely averreſt, […] 1660, Samuel Fisher, “[Rusticus ad Academicos in Exercitationibus Expostulatoriis, Apologeticis Quatuor. The Rustick’s Alarm to the Rabbies: Or, The Country Correcting the University and Clergy, and (Not without Good Cause) Contesting for the Truth, against the Nursing Mothers and Their Children. In Four Apologetical and Expostulatory Exercitations; …] The Third Apologetical, and Expostulatory Exercitation”, in The Testimony of Truth Exalted,[…], [London?: s.n.], published 1679, →OCLC, chapter I, page 411
   [T]he partial Infidel […] averreth the Sleep or Inſenſibility of the Soul both in good and bad perſons, from the time of their Deceaſe hence until their Reſurrection; […] 1701, Lawrence Smith, “[First Discourse on 2 Timothy 1:10]”, in The Evidence of Things Not Seen: Or, The Immortality of the Human Soul, and the Separate Condition thereof in the Other World, Asserted and Made Manifest:[…], London: […] Thomas Speed,[…], →OCLC, page 1
   As Coroner, I must aver, I thoroughly examined her. / And she's not only merely dead, she's really most sincerely dead. 25 August 1939, “Ding-Dong! The Witch Is Dead”, in Yip Harburg (lyrics), Harold Arlen (music), The Wizard of Oz (soundtrack), Metro-Goldwyn-Mayer
   Horticulturalist Richard Lighty has a form [of Trillium grandiflorum] that he avers to open almost a cerise-red. 1997, Frederick W. Case, Jr., Roberta B. Case, “The North American Trilliums”, in Trilliums, Portland, Or.: Timber Press, page 109
   In the meantime, on 5 June 2000, the applicant had brought a civil action against the Prosecutor's Office. He alleged that the termination of his contract had been unlawful and sought reinstatement and compensation for loss of salary. He averred, inter alia, that the climate in the Supreme Cassation Prosecutor's Office had deteriorated as a result of the actions of the Chief Prosecutor. 26 July 2007, European Court of Human Rights (Fifth Section), Peev v. Bulgaria (Application no. 64209/01), Strasbourg, paragraph 19
   [W]hen Yara tells him he picked the losing side, he avers that he might just as soon head back to the Iron Islands—"But first, I'm gonna fuck the queen" … 14 April 2019, Alex McLevy, “Winter is Here on Game of Thrones’ Final Season Premiere (Newbies)”, in The A.V. Club, archived from the original on 2020-12-18
2. (transitive, intransitive, law) To justify or prove (an allegation or plea that one has made).
3. (transitive, obsolete) To avouch, prove, or verify the existence or happening of (something), or to offer to do so.
   [A]lthough thou averrest this, and averrest it truly, we are nevertheless constrained to plead guilty to the possession of so much of this sensibility [a refusal to hear details] (call it "sickly" if thou wilt) as that they case once proved, our feeling of duty refuses to sustain us any longer against that combined and overwhelming influence of shattered nerves and a sickened heart. 1841 December, R[ichard] R[obert] Madden, “Address on Slavery in Cuba, Presented to the General Anti-slavery Convention”, in The Churchman’s Monthly Review, London: R. B. Seeley and W. Burnside; and sold by L. and G. Seeley,[…], →OCLC, page 705

Etymology 2

From 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 (“to have”), from Latin habēre, the present active infinitive of habeō (“to have, hold; to have, own (possessions)”), from Proto-Indo-European *gʰeh₁bʰ-, *ǵʰeh₁bʰ- (“to grab, take”); or * from Old English eafor (“workhorse; tenant’s obligation to transport goods”), further etymology uncertain.

noun

1. (Britain, dialectal, archaic) A beast of burden; chiefly a workhorse, but also a working ox or other animal.
2. (Northern England, Scotland, dialectal, archaic) An old, useless horse; a nag.