avouch vs constate

avouch

verb
  • To confirm or verify, to affirm the validity of. 

  • To declare freely and openly; to assert. 

  • To acknowledge deliberately; to admit; to confess; to sanction. 

  • To appeal to; to cite or claim as authority. 

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 avouch and constate occurred in a corpus of books? (source: Google Ngram Viewer )