cortex vs superficies

cortex

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

  • 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. 

superficies

noun
  • The visible, external surface of a body. 

  • The area of a two-dimensional surface. 

  • The surface (of something immaterial, especially of the mind or soul). 

  • A building intimately associated with the land on which it is built. 

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