rap session vs symposium

rap session

symposium

noun
  • A drinking party in Ancient Greece, especially one with intellectual discussion. 

  • A conference or other meeting for discussion of a topic, especially one in which the participants make presentations. 

  • A collection of essays, articles or papers on a particular subject by a number of contributors. 

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