oblivion vs unconcern

oblivion

noun
  • The state of forgetting completely, of being oblivious, unconscious, unaware, as when sleeping, drunk, or dead. 

  • A form of purgatory. 

  • The state of being completely forgotten, of being reduced to a state of non-existence, extinction, or nothingness, including through war and destruction. (Figuratively) for an area like hell, a wasteland. 

verb
  • To consign to oblivion; to efface utterly. 

unconcern

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

  • Freedom from worry or apprehensiveness; insouciance or nonchalance. 

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