existence vs mortality

existence

noun
  • Empirical reality; the substance of the physical universe. (Dictionary of Philosophy; 1968) 

  • The state of being, existing, or occurring; beinghood. 

mortality

noun
  • The number of deaths per given unit of population over a given period of time. 

  • Death. 

  • Deaths resulting from an event (such as a war, epidemic or disaster). 

  • The state of being susceptible to death. 

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