readership vs symposium

readership

noun
  • The collected readers of a publication. 

  • The role or office of a reader. 

symposium

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

  • 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. 

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