cortex vs pallium

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. 

pallium

noun
  • The cerebral cortex. 

  • The mantle of a mollusc. 

  • A large cloak worn by Greek philosophers and teachers. 

  • A woolen liturgical vestment resembling a collar and worn over the chasuble in the Western Christian liturgical tradition, conferred on archbishops by the Pope, equivalent to the Eastern Christian omophorion. 

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