insouciant

insouciant \in-SOO-see-uhnt\, adjective:

Marked by lighthearted unconcern or indifference; carefree; nonchalant.

The insouciant gingerbread man skips through the pages with glee, until he meets his . . . demise at the end.
-- Judith Constantinides, "The Gingerbread Man", School Library Journal, April 2002

They don't seem to care whether they become stars or not, and their irony . . . has a scoffing, insouciant feel.
-- Thomas Frank, "Pop music in the shadow of irony", Harper's Magazine, March 1998

There's a Steely Dan-ish wit to the title track ("The truth itself is nothing but a gamble/It might or might not set you free"), but Peyroux tosses off the lines with an insouciant shrug of the shoulders.
-- Geoffrey Himes, "Getting to the Heart of It", Washington Post, June 19, 2009

Insouciant is from the French, from in-, "not" + souciant, "caring," present participle of soucier, "to trouble," from Latin sollicitare, "to disturb," from sollicitus, "anxious." The noun form is insouciance.