pillowcase vs tarpaulin

pillowcase

noun
  • A washable, easily removable cloth cover for pillows. 

tarpaulin

noun
  • A tarp, a heavy, waterproof sheet of material, often cloth, used as a cover or blanket. 

  • A hat made of, or covered with, painted or tarred cloth, worn by sailors and others. 

verb
  • To cover with a tarpaulin. 

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