backdrop vs wallcovering

backdrop

noun
  • An image that serves as a visual background. 

  • A decorated cloth hung at the back of a stage. 

  • The setting or background of an acted performance. 

  • Any background situation. 

verb
  • To serve as a backdrop for. 

wallcovering

noun
  • A covering for a wall, such as wallpaper 

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