aplomb

aplomb \uh-PLOM\, noun:

Assurance of manner or of action; self-possession; confidence; coolness.

Then, unexpectedly, she picked up a microphone and began to sing. She sang several songs, handling herself with the aplomb of a professional entertainer.
-- "Rediscovering Japanese Life at a Bike's Pace", New York Times, April 24, 1988

In the jostling hubbub of Tim Hammack's kitchen at the Bay Area Rescue Mission, a homeless shelter in an eddy of urban need, it is about taking life as it comes. It means embracing the unexpected arrival of 200 flats of donated organic strawberries, say, or 600 pounds of bologna with equal culinary aplomb.
-- Patricia Leigh Brown, "Finding Purpose in Serving the Needy, Not Just Haute Cuisine", New York Times, June 13, 2009

His initial broadcasting success was due at least as much to his considerable professional aplomb as it was to his father's broadcasting connections.
-- John A. Jackson, American Bandstand: Dick Clark and the Making of a Rock 'n' Roll Empire

Aplomb is from the French word meaning "perpendicularity, equilibrium, steadiness, assurance," from the Old French phrase a plomb, from a, "according to" (from Latin ad) + plomb, "lead weight" (from Latin plumbum, "lead").