propulsion vs submersion

propulsion

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

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 propulsion and submersion occurred in a corpus of books? (source: Google Ngram Viewer )