borecole vs collard greens

borecole

noun
  • A form of the kale plant, Brassica oleracea acephala, used as the vegetable spring greens / collard greens. 

collard greens

noun
  • A form of Brassica oleracea, sometimes called Brassica oleracea var. acephala or Brassica oleracea var. viridis, similar to kale, that is a popular food in the rural southern United States. 

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