affidavit vs affirmation

affidavit

noun
  • A signed document wherein an affiant makes a sworn statement. 

affirmation

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

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

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

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