backing vs countersignature

backing

adj
  • Providing support for the main performer. 

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. 

countersignature

noun
  • A signature made to confirm or endorse another. 

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