heed vs unconcern

heed

noun
  • Careful attention. 

verb
  • To mind; to regard with care; to take notice of; to attend to; to observe. 

unconcern

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

  • Freedom from worry or apprehensiveness; insouciance or nonchalance. 

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