legitimacy vs permissibility

legitimacy

noun
  • The quality or state of being legitimate or valid; validity. 

  • Lawfulness of birth or origin; directness of descent as affecting the royal succession. 

permissibility

noun
  • The condition of being permissible; legitimacy; allowability. 

  • A permissible act. 

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