apologue vs symbolism

apologue

noun
  • A short story with a moral, often involving talking animals or objects; a fable. 

  • The use of fable to persuade the audience. 

symbolism

noun
  • Representation of a concept through symbols or underlying meanings of objects or qualities. 

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