ennui vs overstrain

ennui

verb
  • To make bored or listless; to weary. 

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

overstrain

verb
  • To subject to an excessive demand on strength, resources, abilities, or the imagination. 

noun
  • excessive strain 

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