approval vs assent

approval

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

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

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

assent

noun
  • agreement; act of agreeing 

verb
  • To agree to a proposal. 

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