affirmation vs countersignature

affirmation

noun
  • That which is affirmed; a declaration that something is true. 

  • A form of self-forced meditation or repetition; autosuggestion. 

  • The solemn declaration made by Quakers and others incapable of taking an oath. 

countersignature

noun
  • A signature made to confirm or endorse another. 

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