allowability vs legitimacy

allowability

noun
  • The state of being allowable; legitimacy; permissibleness. 

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. 

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