colloquium vs rap session

colloquium

noun
  • An address to an academic meeting or seminar. 

  • A colloquy; a meeting for discussion. 

  • An academic meeting or seminar usually led by a different lecturer and on a different topic at each meeting. 

  • That part of the complaint or declaration in an action for defamation which shows that the words complained of were spoken concerning the plaintiff. 

rap session

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