finish off vs send to the glue factory

finish off

verb
  • To kill. 

  • To finish completely. 

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 finish off and send to the glue factory occurred in a corpus of books? (source: Google Ngram Viewer )