prolong vs put off

prolong

verb
  • To put off to a distant time; to postpone. 

  • To lengthen in time; to extend the duration of 

  • To become longer; lengthen. 

  • To extend in space or length. 

put off

verb
  • To delay (a task, event, etc.). 

  • To procrastinate. 

  • To emit; to give off (an odor, smoke, etc.). 

  • To cause to dislike; to discourage (from doing). 

  • To distract; to disturb the concentration of. 

adj
  • daunted or fazed 

  • offended, repulsed 

How often have the words prolong and put off occurred in a corpus of books? (source: Google Ngram Viewer )