lethargy vs unconcern

lethargy

noun
  • A state of extreme torpor or apathy, especially with lack of emotion, energy or enthusiasm; (loosely) sluggishness, laziness. 

  • A condition characterized by extreme fatigue or drowsiness, deep unresponsiveness, or prolonged sleep patterns. 

unconcern

noun
  • Lack of interest or care; indifference or apathy. 

  • Freedom from worry or apprehensiveness; insouciance or nonchalance. 

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