idea vs speculative fiction

idea

noun
  • An image of an object that is formed in the mind or recalled by the memory. 

  • An abstract archetype of a given thing, compared to which real-life examples are seen as imperfect approximations; pure essence, as opposed to actual examples. 

  • A conception in the mind of something to be done; a plan for doing something, an intention. 

  • A purposeful aim or goal; intent 

  • A musical theme or melodic subject. 

  • More generally, any result of mental activity; a thought, a notion; a way of thinking. 

  • A vague or fanciful notion; a feeling or hunch; an impression. 

speculative fiction

noun
  • A particular work belonging to this class. 

  • 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. 

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