put to sleep vs send to the glue factory

put to sleep

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

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

  • To give a general anesthetic prior to surgery. 

  • To cause (someone) to sleep. 

  • To render dormant. 

send to the glue factory

verb
  • To kill, usually a horse. 

  • To retire or remove from prominence, usually due to obsolescence, old age or injury. 

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