potency vs vampirism

potency

noun
  • The ability or capacity to perform something 

  • Concentration; strength 

  • Sexual virility: the ability to become erect or achieve orgasm. 

  • Potentiality, ability, capacity. 

  • Power, authority. 

vampirism

noun
  • extortion 

  • practices associated with vampires, in particular blood-drinking and the draining of a victim's life-force. 

  • Systemic lupus erythematosus (autoimmune disease) 

  • the state of being a vampire 

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