listlessness vs unconcern

listlessness

noun
  • The state of being listless; apathetic indifference; lethargy. 

unconcern

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

  • Freedom from worry or apprehensiveness; insouciance or nonchalance. 

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