doubt vs phlegm

doubt

noun
  • Disbelief or uncertainty (about something); (countable) a particular instance of such disbelief or uncertainty. 

verb
  • To be undecided about; to lack confidence in; to disbelieve, to question. 

phlegm

noun
  • One of the four humors making up the body in ancient and mediaeval medicine; said to be cold and moist, and often identified with mucus. 

  • Calmness of temperament, composure; also seen negatively, sluggishness, indifference. 

  • Viscid mucus produced by the body, later especially mucus expelled from the bronchial passages by coughing. 

  • A watery distillation, especially one obtained from plant matter; an aqueous solution. 

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