aver vs avow

aver

verb
  • To assert the truth of (something); to affirm (something) with confidence; to declare (something) in a positive manner. 

  • To justify or prove (an allegation or plea that one has made). 

avow

verb
  • To declare openly and boldly, as something believed to be right; to own, acknowledge or confess frankly. 

  • To bind or devote by a vow. 

  • To acknowledge and justify, as an act done. See avowry. 

How often have the words aver and avow occurred in a corpus of books? (source: Google Ngram Viewer )