inattention vs unconcern

inattention

noun
  • Lack of attention, or failure to pay attention 

  • An act of neglect; failure of courtesy. 

unconcern

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

  • Freedom from worry or apprehensiveness; insouciance or nonchalance. 

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