hang fire vs kill time

hang fire

verb
  • To wait or hold back. 

  • To fail to fire immediately when the trigger is pulled. 

noun
  • The situation when a gun does not immediately fire when the trigger is pulled, but may fire shortly after. 

kill time

verb
  • To engage in an activity whose only purpose is to make the time seem to pass more quickly; to fill the time between activities. 

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