boscage vs understory

boscage

noun
  • A place set with trees or mass of shrubbery, a grove or thicket. 

  • Among painters, a picture depicting a wooded scene. 

  • Mast-nuts of forest trees, used as food for pigs, or any such sustenance as wood and trees yield to cattle. 

  • A tax on wood. 

understory

noun
  • The layer of plants that grow in the shade of the canopy of a forest. 

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