boniato vs white sweet potato

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). 

white sweet potato

noun
  • A variety of sweet potato (Ipomoea batatas) that has a relatively white skin and flesh 

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