sit-in vs sleep-in

sit-in

noun
  • A peaceful form of protest in which people occupy an area and refuse to leave. 

adj
  • Designed to be sat in. 

sleep-in

noun
  • An instance of sleeping in, sleeping late, sleeping until one feels fully refreshed rather than rising at a prespecified time. 

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