cold feet vs trepidation

cold feet

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

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

trepidation

noun
  • A fearful state; a state of concern or hesitation. 

  • An involuntary trembling, sometimes an effect of paralysis, but usually caused by terror or fear. 

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