enervation vs ennui

enervation

noun
  • State of being enervated; debility. 

  • Act of enervating; debilitation. 

ennui

noun
  • A gripping listlessness or melancholia caused by boredom; depression. 

verb
  • To make bored or listless; to weary. 

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