allegory vs litotes

allegory

noun
  • A symbolic representation which can be interpreted to reveal a hidden meaning, usually a moral or political one. 

  • A narrative in which a character, place, or event is used to deliver a broader message about real-world issues and occurrences. 

  • A picture, book, or other form of communication using such representation. 

  • A category that retains some of the structure of the category of binary relations between sets, representing a high-level generalisation of that category. 

litotes

noun
  • An ironic figure of speech whereby something is stated by denying its opposite, particularly the negation of a negative quality to say something positive. 

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