insist vs interrogate

insist

verb
  • To demand continually that something happen or be done; to reiterate a demand despite requests to abandon it. 

  • To hold up a claim emphatically. 

interrogate

verb
  • to question or quiz, especially in a thorough and/or aggressive manner 

  • to examine critically. 

  • to query; to request information from. 

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