EtymEx

nonchalant

/ˌnɑnʃəˈlɑnt/adjective, adverb

calmly unconcerned or showing little interest

From Latin, via Old French and English non- (not) + O.French, from Latin calēre chaloir (to have concern for).

Lineage

non-

chaloir

LatinRomanceGermanicnot directly attestedSelect a stage for details, or drag it

The story

There is a little temperature shift hidden inside this cool-sounding word: Latin calēre meant “to be hot,” and its French descendant chaloir came to mean “to care about.” Add non-, “not,” and French speakers had nonchaloir—literally, not to care. English borrowed nonchalant from French, with the word recorded in 1734. The same French root appears in chaland, meaning “customer” or “client”—someone with an interest in buying. So a nonchalant person is, etymologically, someone who has let the heat of concern go out.

Modern usage

Indifferent or uninterested, sometimes notably calm in a tense situation.

Heard in
informal usage · online slang
See
Urban Dictionary entries describing an unconcerned demeanor

Related words

Words from the same roots

non- · Latin, via Old French and English, ‘not; absence of or negation of something’

Derivednonconformist, non-consensual, nonfiction, nonsense

chaloir · Old French, from Latin calēre, ‘to have concern for; ultimately “to be hot”’

Derivedchaland, nonchalant

Sources