firebrand vs instigator

firebrand

noun
  • An argumentative troublemaker or revolutionary; one who agitates against the status quo. 

  • A torch or other burning stick with a flame at one end. 

instigator

noun
  • A person who intentionally instigates, incites, or starts something, especially one that creates trouble. 

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