mung bean vs vetch

mung bean

noun
  • The seed of Vigna radiata, native to South Asia. 

vetch

noun
  • Any of several leguminous plants, of the genus Vicia, often grown as green manure and for their edible seeds. 

  • Any of several similar plants within the subfamily Faboideae. 

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