kill time vs loiter

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. 

loiter

verb
  • To remain at a certain place instead of moving on. 

  • To stand about without any aim or purpose; to stand about idly. 

  • For an aircraft to remain in the air near a target. 

noun
  • A standing or strolling about without any aim or purpose. 

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