crack up vs lose the plot

crack up

verb
  • To cry up; to extol. 

  • To cause to laugh heartily. 

  • To become insane; to suffer a mental breakdown. 

  • To crash an aircraft or automobile. 

  • To laugh heartily. 

adj
  • Funny; hilarious 

lose the plot

verb
  • Used other than figuratively or idiomatically: see lose, plot. 

  • To lose sight of an important objective or principle; to act contrarily to one's own interests through concentrating on relatively unimportant matters. 

  • To cease to behave in a consistent and/or rational manner. 

How often have the words crack up and lose the plot occurred in a corpus of books? (source: Google Ngram Viewer )