avow vs constate

avow

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

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

  • To bind or devote by a vow. 

constate

verb
  • To ascertain; to verify; to establish; to prove. 

  • To relay information in a statement and say whether it is true or false. 

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