hang up one's boots vs send to the glue factory

hang up one's boots

verb
  • retire, call it a day 

send to the glue factory

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

  • To kill, usually a horse. 

How often have the words hang up one's boots and send to the glue factory occurred in a corpus of books? (source: Google Ngram Viewer )