disinterest vs unconcern

disinterest

noun
  • An absence of interest (attention or curiosity). 

  • The absence of interest (bias or stake). 

verb
  • To render disinterested. 

unconcern

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

  • Freedom from worry or apprehensiveness; insouciance or nonchalance. 

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