durra vs sorghum

durra

noun
  • A kind of millet, a variety of sorghum; Indian millet (Sorghum bicolor). 

sorghum

noun
  • A cereal, Sorghum genus and species, the grains of which are cultivated to make flour and feed cattle. Almost all cultivated ones as well as some wild ones belong to the species Sorghum bicolor (syn. Sorghum vulgare). 

  • Sorghum syrup. 

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