chillum vs gravity bong

chillum

noun
  • A conical pipe used for smoking marijuana, usually made of fired clay, porcelain, soapstone, glass or, more rarely, wood. 

  • The part of such a pipe that contains the tobacco and charcoal balls. 

gravity bong

noun
  • A homemade device used to smoke marijuana, consisting of a plastic jug with the bottom cut out and immersed in a vat of water, which is then raised to create a vacuum beneath its bowl of lit marijuana. 

  • Synonym of waterfall bong 

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