go off vs go to sleep

go off

verb
  • To pass off; to take place; to be accomplished. 

  • To explode metaphorically; to become very angry. 

  • To putrefy or become inedible, or to become unusable in any way. 

  • To fire, especially accidentally. 

  • To begin clanging or making noise. 

  • To explode. 

  • To depart; to leave. 

  • To like less. 

  • (chiefly UK, of epoxy resins) To cure; to set. 

  • To ejaculate. 

  • To stop operating; to switch off. 

go to sleep

verb
  • To die. 

  • To be affected by paresthesia; to go numb. 

  • To fall asleep. 

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