catnap vs sleep in

catnap

verb
  • To take a catnap (short sleep or nap). 

  • To kidnap a cat. 

noun
  • A brief, light sleep, usually during the daytime. 

sleep in

verb
  • To sleep late; to go on sleeping past one's customary or planned hour. 

  • Used other than figuratively or idiomatically: see sleep, in. 

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