chlorophyll vs leaf vegetable

chlorophyll

noun
  • Any of a group of green pigments that are found in the chloroplasts of plants and in other photosynthetic organisms such as cyanobacteria. 

leaf vegetable

noun
  • The leaf of a plant used as an edible vegetable, such as lettuce, spinach, or rocket. 

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