fire in the belly vs spunk

fire in the belly

noun
  • The emotional stamina and vigor, passion, or inner drive to achieve something, to take action, etc. 

spunk

noun
  • Courage; spirit; mettle; determination. 

  • An attractive person (normally male). 

  • Touchwood; tinder. 

  • Semen. 

verb
  • To ejaculate. 

  • To waste (money etc.). 

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