fall asleep vs go to sleep

fall asleep

verb
  • To be affected by paresthesia; to go numb. 

  • To pass from a state of wakefulness into sleep. 

  • To die (often seen on gravestones). 

go to sleep

verb
  • To be affected by paresthesia; to go numb. 

  • To fall asleep. 

  • To die. 

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