lie-in vs teach-in

lie-in

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

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

teach-in

noun
  • An extended session of lectures or discussions on controversial topics as a form of protest. 

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