cobbler, keep to your last vs shoemaker

cobbler, keep to your last

proverb
  • Do not criticise matters outside your field of expertise; mind your own business. 

shoemaker

noun
  • The threadfish. 

  • A fish, Elagatis pinnulatis, the runner. 

  • A person who makes shoes 

How often have the words cobbler, keep to your last and shoemaker occurred in a corpus of books? (source: Google Ngram Viewer )