black cod vs pollock

black cod

noun
  • Synonym of sablefish (Anoplopoma fimbria); (the sablefish is not a species of codfish; but is referred to as cod informally) 

pollock

noun
  • Either of two lean, white marine food fishes, of the genus Pollachius, in the cod family. 

verb
  • To fish for pollock. 

  • To splatter, as with paint. 

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