black cod vs saithe

black cod

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

saithe

noun
  • The pollock or coalfish or coley (Pollachius virens). 

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