flatulence vs fossil fuel

flatulence

noun
  • The release of such gas; breaking wind. 

  • The state of having gas, often smelly, trapped (and when released, frequently with noise) in the digestive system of a human and some other animals; wind; and when released, a flatus, a fart. 

fossil fuel

noun
  • Any fuel derived from hydrocarbon deposits such as coal, petroleum, natural gas and, to some extent, peat; these fuels are non-renewable, and their burning moves carbon from underground into the atmosphere via the greenhouse gas carbon dioxide. 

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