lassitude vs slowness

lassitude

noun
  • Lethargy or lack of energy; fatigue. 

  • Listlessness or languor. 

slowness

noun
  • The quality or state of being slow. 

  • A unit, the reciprocal of velocity, that delineates the amount of time required for an object to travel a given distance. 

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