polymorphous vs shapeshifting

polymorphous

adj
  • Having, or occurring in, several distinct forms 

  • Crystallizing in two or more different forms; polymorphic 

  • Having, or assuming, a variety of forms, characters, or styles 

shapeshifting

noun
  • A change in shape; a transformation. 

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