nonchalance vs watchfulness

nonchalance

noun
  • Indifference, unconcern; carelessness; coolness; disregard, detachment. 

watchfulness

noun
  • The state or quality of being watchful; alertness, vigilance or wakefulness. 

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