cold feet vs unconcern

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. 

unconcern

noun
  • Lack of interest or care; indifference or apathy. 

  • Freedom from worry or apprehensiveness; insouciance or nonchalance. 

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