cistern vs keg

cistern

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

  • The vessel surrounding the condenser in a steam engine. 

  • A cisterna. 

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

keg

noun
  • A round, traditionally wooden container of lesser capacity than a barrel, often used to store beer. 

verb
  • To store in a keg. 

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