affirmation vs protestation

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. 

protestation

noun
  • A declaration in common-law pleading, by which the party interposes an oblique allegation or denial of some fact, protesting that it does or does not exist, and at the same time avoiding a direct affirmation or denial. 

  • a formal solemn objection or other declaration 

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