letting vs verification

letting

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

  • Synonym of tenancy. 

verification

noun
  • The state of being verified. 

  • Confirmation; authentication. 

  • A formal phrase used in concluding a plea, to denote confirmation by evidence. 

  • The operation of testing the equation of a problem, to see whether it truly expresses the conditions of the problem. 

  • The act of verifying. 

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