Insouciance [in-SOO-see-əns]  

Part of speech: noun 

Origin: French, late 18th century  

1. Casual lack of concern; indifference.  

Examples of insouciance in a sentence  

"I admire my partner’s insouciance toward traffic and other things that annoy me."  

"During the last week of school, the children showed insouciance toward any lessons."