aqua vs light water

aqua

noun
  • The compound water. 

  • A shade of colour, usually a mix of blue and green similar to the colour turquoise. 

adj
  • Of a greenish-blue colour. 

light water

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

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

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