Nonchalance
Etymology
A French borrowing, from "nonchalant," built on non- (not) and "chaloir" (to matter, to be of concern), which descends from Latin "calere" (to be warm, to be heated). The literal image is of not being "warmed" or stirred by something — coolness in the emotional sense. English kept both the word and its unmistakably French poise.
noun · /NON-shuh-lahns/
A relaxed, unconcerned manner; casual indifference.
What it names
Studied coolness — the poised air of not caring, which may be genuine ease or a carefully worn mask.
Example
He accepted the award with a nonchalance that suggested he won them all the time.
Related idea
Apathy is a genuine absence of caring; nonchalance is the poised appearance of not caring, whether or not one actually does.
See also