inexistence vs infrequency

inexistence

noun
  • The state of not being, not existing, or not being perceptible. 

  • The state of existing in something 

  • That which exists within; a constituent. 

infrequency

noun
  • The state of being unfrequented; isolation; seclusion. 

  • The characteristic of being infrequent. 

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