backdrop vs flats

backdrop

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

  • An image that serves as a visual background. 

  • The setting or background of an acted performance. 

  • Any background situation. 

verb
  • To serve as a backdrop for. 

flats

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