flooding vs propulsion

flooding

noun
  • A form of therapy that treats a phobia by suddenly exposing the patient to the object of the phobia, instead of approaching it gradually. 

  • An act of flooding; a flood or gush. 

  • Emotional overwhelm sometimes leading to a primal state of rage or panic. 

propulsion

noun
  • The action of driving or pushing, typically forward or onward; a propulsive force or impulse. 

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