ermine vs ferret

ermine

noun
  • A weasel found in northern latitudes (Mustela erminea in Eurasia, Alaska, and the Arctic, Mustela haidarum in Haida Gwaii, Mustela richardsonii in the rest of North America); its dark brown fur turns white in winter, apart from the black tip of the tail. 

  • A white field with black spots. 

  • The white fur of this animal, traditionally seen as a symbol of purity and used for judges' robes. 

  • Any of various moths, especially in the family Yponomeutidae 

  • The office of a judge. 

adj
  • In blazon, of the colour ermine (white with black spots). 

verb
  • To clothe with ermine. 

ferret

noun
  • The black-footed ferret, Mustela nigripes. 

  • A diligent searcher. 

  • An often domesticated mammal (Mustela putorius furo) rather like a weasel, descended from the polecat and often trained to hunt burrowing animals. 

verb
  • To uncover and bring to light by searching; usually to ferret out. 

  • To hunt game with ferrets. 

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