Nonchalant

/ˌnɑːnʃəˈlɑːnt/ adjective easy

Coolly unconcerned or casual, as if nothing could bother you.

She gave a nonchalant shrug when told her flight had been cancelled.

Memory Trick

French roots: 'non' (not) plus 'chaloir' (to be concerned) — nonchalant literally means 'not concerned.'