engrossment vs intrusive thought

engrossment

noun
  • The state of being engrossed; concentration or preoccupation. 

  • The fact or instance of preparing the final draft legal document for execution or completion. 

  • Such document that has not yet been executed or completed. 

intrusive thought

noun
  • an unwelcome involuntary thought, image or idea 

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