ocarina vs sweet potato

ocarina

noun
  • A woodwind musical instrument that is closed at both sides to produce an enclosed space, and punctured with finger holes. 

sweet potato

noun
  • The tuber of this plant cooked as a vegetable. 

  • An ocarina. 

  • A tropical perennial American vine, Ipomoea batatas, having a fleshy tuber. 

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