blue heeler vs burgomaster

blue heeler

noun
  • A police officer. 

  • A blue-coated variety of the Australian Cattle Dog breed. 

burgomaster

noun
  • The mayor, or head magistrate, of a town in the Netherlands, Belgium, Germany and certain other countries. 

How often have the words blue heeler and burgomaster occurred in a corpus of books? (source: Google Ngram Viewer )