cistern vs pocket billiards

cistern

noun
  • A reservoir or tank for holding water, especially for catching and holding rainwater for later use. 

  • The vessel surrounding the condenser in a steam engine. 

  • In a flush toilet, the container in which the water used for flushing is held; a toilet tank. 

  • A cisterna. 

pocket billiards

noun
  • Synonym of pocket pool 

  • Any of a family of billiards games played on a specific class of billiards table, having six receptacles called pockets along the rails, in which balls are deposited as the main goal of play. 

How often have the words cistern and pocket billiards occurred in a corpus of books? (source: Google Ngram Viewer )