ennui vs prosaicness

ennui

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

verb
  • To make bored or listless; to weary. 

prosaicness

noun
  • The characteristic of being prosaic. 

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