cask vs cistern

cask

noun
  • A large barrel for the storage of liquid, especially of alcoholic drinks. 

verb
  • To put into a cask. 

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. 

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