green bean vs mung bean

green bean

noun
  • The immature pods of any kind of bean plant, eaten as a vegetable. 

  • The immature pods of numerous varieties of the common bean, Phaseolus vulgaris. 

mung bean

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

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