corium vs rhizodermis

corium

noun
  • The deep layer of mucous membranes beneath the epithelium. 

  • The layer of skin between the epidermis and the subcutaneous tissues; the dermis. 

  • A lavalike mixture of fissile material created in a nuclear reactor's core during a nuclear meltdown. 

  • Armour made of leather, particularly that used by the Romans. 

rhizodermis

noun
  • The outermost primary cell layer of the root. 

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