covers vs nightclothes

covers

noun
  • The bedclothes; collectively, the sheets, blankets, etc. 

  • The tarpaulins or other devices used to cover the wicket during rain, in order to prevent it getting wet. 

  • The area of the field near cover and extra cover. 

nightclothes

noun
  • Clothing worn while sleeping in bed, such as pyjamas or a nightgown, and, when worn over nightclothes, a robe. 

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