caution vs unconcern

caution

verb
  • To warn; to alert, advise that caution is warranted. 

  • To give a yellow card 

noun
  • A formal warning given as an alternative to prosecution in minor cases. 

  • Security; guaranty; bail. 

  • A yellow card. 

  • Prudence when faced with, or when expecting to face, danger; care taken in order to avoid risk or harm. 

  • A careful attention to the probable effects of an act, in order that failure or harm may be avoided. 

unconcern

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

  • Freedom from worry or apprehensiveness; insouciance or nonchalance. 

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