nonchalance vs solicitude

nonchalance

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

solicitude

noun
  • The state of being solicitous; uneasiness of mind occasioned by fear of evil or desire for good; anxiety. 

  • Special or pronounced concern or attention. 

  • A cause of anxiety or concern. 

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