dejection vs unhappiness

dejection

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

  • The act of humbling or abasing oneself. 

  • A low condition; weakness; inability. 

unhappiness

noun
  • The feeling of not being happy 

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