figment of one's imagination vs imagination

figment of one's imagination

noun
  • A product of the imagination. 

imagination

noun
  • A mental image formed by the action of the imagination as a faculty; something imagined. 

  • Particularly, construction of false images; fantasizing. 

  • Creativity; resourcefulness. 

  • The image-making power of the mind; the act of mentally creating or reproducing an object not previously perceived; the ability to create such images. 

How often have the words figment of one's imagination and imagination occurred in a corpus of books? (source: Google Ngram Viewer )