litotes vs synecdoche

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. 

synecdoche

noun
  • The use of this figure of speech. 

  • A figure of speech that uses the name of a part of something to represent the whole, or the whole to represent a part. 

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