bedsheet vs comforter

bedsheet

noun
  • A sheet, a piece of cloth cut and finished as bedlinen. 

comforter

noun
  • A padded cover for a bed, duvet, continental quilt. 

  • A pacifier. 

  • A person who comforts someone who is suffering. 

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