letting vs permission

letting

noun
  • Synonym of tenancy. 

  • Hyponyms: sublease, underlease, subtenancy, undertenancy, subletting, underletting, (informal) sublet, underlet 

permission

noun
  • The act of permitting. 

  • authorisation; consent (especially formal consent from someone in authority) 

  • Flags or access control lists pertaining to a file that dictate who can access it, and how. 

verb
  • To grant or obtain authorization for. 

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