12 vs Old Bill

12

noun
  • Collectively, police or law enforcement. 

  • See also: fuck 12 

symbol
  • Used by fans of American football, positioning themselves as the 12th member of an 11-player team. 

Old Bill

noun
  • The police force. 

  • A police officer. 

How often have the words 12 and Old Bill occurred in a corpus of books? (source: Google Ngram Viewer )