boniato vs ipomoea

boniato

noun
  • A Cuban type of sweet potato with light-colored flesh that is drier and less sweet than the varieties typical in the US (Ipomoea batatas). 

ipomoea

noun
  • Any of various twining plants of the genus Ipomoea with showy monopetalous flowers, including the morning glory, the sweet potato, and the cypress vine. 

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