approval vs endorsement

approval

noun
  • An expression of favorable acceptance and encouragement; a compliment that also condones. 

  • Something mailed by a seller to a collector to match their stated interests; the collector can approve of or return the item. 

  • An expression granting permission; an indication of agreement with a proposal; an acknowledgement that a person, thing, or event meets requirements. 

endorsement

noun
  • The act or quality of endorsing 

  • Sponsorship, in means of money, by a company, business or enterprise. 

  • An amendment or annotation to an insurance contract or other official document (such as a driving licence). 

  • An instructor's signed acknowledgement of time practising specific flying skills. 

  • Permission to carry out a specific skill or application in a field in which the practitioner already has a general licence. 

  • Support from an important, renowned figure of a media (celebrity, politics, sports, etc.), to get back up. 

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