unconcern vs unenthusiasm

unconcern

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

  • Freedom from worry or apprehensiveness; insouciance or nonchalance. 

unenthusiasm

noun
  • Lack of enthusiasm. 

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