affirmation vs certification

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. 

certification

noun
  • The act of certifying. 

  • The granting of a certificate. 

  • A professional qualification that certifies a person's ability. 

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