ennui vs sleepiness

ennui

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

verb
  • To make bored or listless; to weary. 

sleepiness

noun
  • The property of being sleepy. 

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