byword vs cush-cush

byword

noun
  • A proverb or proverbial expression, common saying; a frequently used word or phrase. 

  • A nickname or epithet. 

  • Someone or something that stands as an example (i.e. metonymically) for something else, by having some of that something's characteristic traits. 

  • A characteristic word or expression; a word or phrase associated with a person or group. 

  • An object of notoriety or contempt, scorn or derision. 

cush-cush

noun
  • Synonym of couche-couche 

  • A tropical American yam with small yellow-skinned edible tubers: Dioscorea trifida 

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