bittern vs egret

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). 

egret

noun
  • Any of various wading birds of the genera Egretta or Ardea that includes herons, many of which are white or buff, and several of which develop fine plumes during the breeding season. 

  • A plume or tuft of feathers worn as a part of a headdress, or anything imitating such an ornament. 

  • The flying feathery or hairy crown of seeds or achenes, such as the down of the thistle. 

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