Dioscorea trifida vs cush-cush

Dioscorea trifida

cush-cush

noun

  • Synonym of couche-couche 

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

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