flooding vs submersion

flooding

noun
  • An act of flooding; a flood or gush. 

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

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

submersion

noun
  • The act of submerging, or the state of being submerged; immersion 

  • A differentiable map whose differential is everywhere surjective. 

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