fur seal vs seadog

fur seal

noun
  • A marine mammal of either of the genera Arctocephalus or Callorhinus of the eared seal family Otariidae, differing from the sea lions in having dense underfur. 

seadog

noun
  • A dogfish. 

  • A charge resembling the talbot but with scales, webbed feet and a broad tail. 

  • A sailor accustomed to the sea. 

  • An omen of bad luck. 

  • A white-topped wave in an estuary. 

  • A pirate. 

  • A fogbow, as seen my mariners. 

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