overstrain vs put to sleep

overstrain

noun
  • excessive strain 

verb
  • To subject to an excessive demand on strength, resources, abilities, or the imagination. 

put to sleep

verb
  • To help (someone) to bed; put to bed. 

  • To kill an animal painlessly, often with an injection; to euthanize. 

  • To give a general anesthetic prior to surgery. 

  • To cause (someone) to sleep. 

  • To render dormant. 

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