Pirate vs sea rat

Pirate

noun
  • someone connected with any of a number of sports teams known as the Pirates, as a fan, player, coach etc. 

  • someone connected with Bristol Rovers Football Club, as a fan, player, coach etc. 

sea rat

noun
  • A pirate. 

  • A fish, the chimaera. 

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