NONCHALANTLY

casually, nonchalantly

(adverb) in an unconcerned manner; “glanced casually at the headlines”

coolly, nervelessly, nonchalantly

(adverb) in a composed and unconcerned manner; “without more ado Barker borrowed a knife from his brigade Major and honed it on a carborundum stone as coolly as a butcher”

Source: WordNet® 3.1

Etymology

Adverb

nonchalantly (comparative more nonchalantly, superlative most nonchalantly)

In a nonchalant manner.

Source: Wiktionary

Non"cha*lant`ly, adv.

Definition: In a nonchalant, indifferent, or careless manner; coolly.

NONCHALANT

Non`cha`lant", a. Etym: [F., fr. non not (L. non) + chaloir to concern one's self for, fr. L. calere to be warm, to be inflamed with desire, to be troubled. See Non-, and Caldron.]

Definition: Indifferent; careless; cool.

Source: Webster’s Unabridged Dictionary 1913 Edition