caustic soda vs fizzy water

caustic soda

noun
  • sodium hydroxide (NaOH), a strong alkaline substance used in the manufacture of paint, soap and detergents, or as a drain cleaner. 

fizzy water

noun
  • carbonated water. 

  • Any carbonated, usually sweet, non-alcoholic drink; a soft drink. 

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