pugnacity vs slow burn

pugnacity

noun
  • The act or characteristic of being aggressive or combative. 

slow burn

noun
  • A gradually increasing feeling of anger or frustration. 

  • A romantic story (especially a work of fan fiction) in which the central relationship develops slowly. 

adj
  • Developing slowly over the course of the story. 

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