bast vs cortex

bast

noun
  • Fibre made from the phloem of certain plants and used for matting and cord. 

cortex

noun
  • The tissue of a stem or root that lies inward from the epidermis, but exterior to the vascular tissue. 

  • The outer surface of a piece of flint. 

  • The outer layer of an internal organ or body structure, such as the kidney or the brain. 

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