butter bean vs green bean

butter bean

noun
  • Any of several beans, including the lima bean, sieva bean, wax bean, and civet bean. 

green bean

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

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

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