diprotium monoxide vs seawater

diprotium monoxide

noun
  • A humorous chemical name for "water." 

seawater

noun
  • The saltwater of a sea or ocean. 

adj
  • Associated in some way with seawater, or intended for dealing with seawater. 

  • Consisting of seawater. 

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