mustelid vs serpent

mustelid

noun
  • Any carnivorous mammal of the diverse weasel family Mustelidae, which also includes badgers, otters, martens, mink and wolverines. 

serpent

noun
  • A snake, especially a large or dangerous one. 

  • An obsolete wind instrument in the brass family, whose shape is suggestive of a snake (Wikipedia article). 

  • A kind of firework with a serpentine motion. 

  • A subtle, treacherous, malicious person. 

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