indifference vs lassitude

indifference

noun
  • Unemotional apathy. 

  • Unconcerned nonchalance. 

  • The state of being indifferent. 

  • Unbiased impartiality. 

  • Self-identity defined through the negation of difference, non-difference. 

  • A lack of enthusiasm. 

lassitude

noun
  • Listlessness or languor. 

  • Lethargy or lack of energy; fatigue. 

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