malodor vs mephitis

malodor

noun
  • An offensive odor. 

mephitis

noun
  • A poisonous or foul-smelling gas, especially as emitted from the earth; an unpleasant smell. 

  • A dilution of fluids derived from skunks or polecats. 

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