kumara vs sweet potato

kumara

noun

  • A sweet potato. 

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 kumara and sweet potato occurred in a corpus of books? (source: Google Ngram Viewer )