coalfish vs saithe

coalfish

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

saithe

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

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