aver vs vow

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). 

vow

verb
  • To make a vow regarding (something). 

  • To declare publicly that one has made a vow, usually to show one's determination or to announce an act of retaliation. 

  • To make a vow; to promise. 

noun
  • A solemn promise to perform some act, or behave in a specified manner, especially a promise to live and act in accordance with the rules of a religious order. 

  • A declaration or assertion. 

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