dejection vs ennui

dejection

noun
  • A state of melancholy or depression; low spirits, the blues. 

  • The act of humbling or abasing oneself. 

  • A low condition; weakness; inability. 

ennui

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

verb
  • To make bored or listless; to weary. 

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