nonchalance

[ non-shuh-lahns, non-shuh-lahns, -luh ns ]

/ ˌnɒn ʃəˈlɑns, ˈnɒn ʃəˌlɑns, -ləns /

the state or quality of being nonchalant; cool indifference or lack of concern; casualness.

Origin of nonchalance

From French, dating back to 1670–80; see origin at nonchalant, -ance

I thought his nonchalance suggested that he failed to grasp the gravity of his situation.

In His First Interview, Saif al-Islam Says He Has Not Been Given Access to a Lawyer |Fred Abrahams |December 30, 2011 |DAILY BEAST
This is not a time to manipulate or skulk into situations sideways, attempting to give a false impression of nonchalance.

Your Week: What the Stars Hold |Starsky + Cox |September 4, 2011 |DAILY BEAST
Authentic beauty comes when something precious is treated with nonchalance—even disrespect, perhaps even a bit of abuse.

Amy Winehouse’s Broken Beauty |Robin Givhan |July 26, 2011 |DAILY BEAST
Cheerfulness requires something more than a well-balanced Rabelaisian nonchalance in adversity and a keen relish for all pleasure.

The Continental Monthly, Vol. 3 No 2, February 1863 |Various

Blacklock tried hard to assume the manly attitude of nonchalance; tried and failed utterly.

The King of Arcadia |Francis Lynde
She would defeat him again with her calm and her nonchalance, just as she had done this time.

A Fair Mystery |Bertha M. Clay
Perhaps it was his mastery of the situation that gave him unconsciously a rock-like air of nonchalance.

The Street Called Straight |Basil King
Bud caught his breath, for obviously Gram had seen through Gramps' nonchalance.

The Black Fawn |James Arthur Kjelgaard