knacker's yard vs pigsty

knacker's yard

noun
  • The area of a slaughterhouse where carcasses unfit for human consumption or other purposes are rendered down to produce useful materials such as glue. 

  • A (notional) place to send a person or object that is spent beyond all reasonable use. 

pigsty

noun
  • An enclosure where pigs are kept. 

  • A dirty or very untidy place. 

How often have the words knacker's yard and pigsty occurred in a corpus of books? (source: Google Ngram Viewer )