fairy tale vs speculative fiction

fairy tale

noun
  • A folktale featuring fairies or similar fantasy characters. 

  • A delightful and ideal situation of a kind attained by very few. 

  • A story presented as true that is not believable. 

speculative fiction

noun
  • A class of fiction involving fantastic, supernatural or futuristic elements, including fantasy, horror, and science fiction, dealing with worlds, themes, and characters not part of everyday life. 

  • A particular work belonging to this class. 

How often have the words fairy tale and speculative fiction occurred in a corpus of books? (source: Google Ngram Viewer )