black bag vs nuclear football

black bag

noun
  • The pouch or case traditionally carried by medical doctors, especially when making house calls, and containing medical instruments and supplies. 

  • A pouch or case containing burglary tools. 

  • A black plastic sack produced for the disposal of household waste. 

nuclear football

How often have the words black bag and nuclear football occurred in a corpus of books? (source: Google Ngram Viewer )