butterfish vs skil

butterfish

noun
  • The sablefish (Anoplopoma fimbria) (the sablefish is not a true butterfish; but is called such informally) 

  • Perciform fish of the family Stromateidae, including the genera Pampus, Peprilus and Stromateus. 

  • A rock gunnel, Pholis gunnellus, an eel-like fish found in the intertidal and subtidal zones of the North Atlantic. 

  • The New Zealand fish Odax pullus, also known as greenbone. 

skil

noun
  • Synonym of sablefish 

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