cold feet vs heroism

cold feet

noun
  • Used other than figuratively or idiomatically: see cold, feet. 

  • A feeling of nervousness or anxiousness causing one to reconsider a decision about an upcoming event. 

heroism

noun
  • The qualities characteristic of a hero, such as courage, bravery, fortitude, selflessness, etc.; the display of such qualities. 

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