boil up vs fire up

boil up

verb
  • To become more excited, intense or exciting. 

  • To cook or prepare by boiling. 

noun
  • A traditionally Maori soup/stew made with potatoes, pork and other ingredients. 

fire up

verb
  • To excite; to infuse with energy. 

  • Of an engine or similar, to start. 

  • To ignite. 

  • To launch; to run. 

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