heedlessness vs insouciance

heedlessness

noun

  • The state or character of being heedless 

insouciance

noun

  • Carelessness, heedlessness, indifference, or casual unconcern. 

  • Nonchalance. 

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