deluge vs light water

deluge

noun
  • A system for flooding or drenching a space, container, or area with water in an emergency to prevent or extinguish a fire. 

  • A great flood or rain. 

  • An overwhelming amount of something; anything that overwhelms or causes great destruction. 

verb
  • To flood with water. 

  • To overwhelm. 

light water

noun
  • Foam formed by water and a fluorocarbon surfactant, used in firefighting because it floats on flammable liquids lighter than water. 

  • Water in its standard form of H₂O, containing two protium hydrogen atoms, as opposed to heavy water. 

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