avouch vs mean to say

avouch

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

  • To declare freely and openly; to assert. 

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

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

mean to say

verb
  • To imply or intend to convey with one's words; used to correct or clarify one's previous utterance, or to seek such clarification. 

How often have the words avouch and mean to say occurred in a corpus of books? (source: Google Ngram Viewer )