lassitude vs stagnation

lassitude

noun
  • Listlessness or languor. 

  • Lethargy or lack of energy; fatigue. 

stagnation

noun
  • Inactivity. 

  • The state of being stagnant, without circulation. 

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