lie-in vs sleep-in

lie-in

noun
  • A period spent lying in bed for longer than usual after one has woken up. 

  • A form of protest where a group of people lie down in a public area. 

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 lie-in and sleep-in occurred in a corpus of books? (source: Google Ngram Viewer )