approval vs backing

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. 

backing

noun
  • Support, especially financial. 

  • A backdrop. 

  • The mounting of a horse or other animal. 

  • The action of putting something back; a switching into reverse. 

  • A liner or other material added behind or underneath. 

  • Musicians and vocalists who support the main performer. 

adj
  • Providing support for the main performer. 

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