go to sleep vs kip down

go to sleep

verb
  • To fall asleep. 

  • To be affected by paresthesia; to go numb. 

  • To die. 

kip down

verb
  • To sleep somewhere other than home, forced to do so by circumstances. 

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