coalfish vs sea lettuce

coalfish

noun
  • any of several blackish fish, especially Pollachius virens, a pollack, and Anoplopoma fimbria, sablefish. 

sea lettuce

noun
  • Scaevola taccada, also known as the beach cabbage, a terrestrial flowering plant species that is native to coastal regions of the Indo-Pacific. 

  • Monostroma spp., also known as the slender sea lettuce, a kind of algae. 

  • Dudleya caespitosa, also known as the sand lettuce, a terrestrial flowering plant species that is endemic to coastal areas of California 

  • Similar seaweed species of other genera 

  • Any of several edible seaweeds of the genus Ulva. 

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