enervation vs melancholy

enervation

noun
  • State of being enervated; debility. 

  • Act of enervating; debilitation. 

melancholy

adj
  • Affected with great sadness or depression. 

noun
  • Great sadness or depression, especially of a thoughtful or introspective nature. 

  • Black bile, formerly thought to be one of the four "cardinal humours" of animal bodies. 

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