bittern vs heron

bittern

noun
  • Several bird species in the Botaurinae subfamily of the heron family Ardeidae. 

  • The saline substance added to soy milk to coagulate it as a primary step in the production of tofu. 

  • The liquor remaining after halite (common salt) has been harvested from saline water (brine). 

heron

noun
  • A long-legged, long-necked wading bird of the family Ardeidae. 

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