1650s, "dexterous," originally "rightly," from French adroit, which by Old French had senses "upright (physically and morally); able, clever, skillful; well-formed, handsome; on the right-hand side; veritable," from adverbial phrase à droit "according to right."
This is from Old French à "to" (see ad-) + droit, dreit "right," from Medieval Latin directum (contracted drictum) "right, justice, law," neuter or accusative of Latin directus "straight," past participle of dirigere "set straight," from dis- "apart" (see dis-) + regere "to direct, to guide, keep straight" (from PIE root *reg- "move in a straight line," with derivatives meaning "to direct in a straight line," thus "to lead, rule"). It expresses prominently the idea of a trained hand. Related: Adroitly; adroitness.
"pertaining to atoms," 1670s as a philosophical term (see atomistic); scientific sense dates from 1811, from atom + -ic. Atomic number is from 1821; atomic mass is from 1848. Atomic energy first recorded 1906 in modern sense (as intra-atomic energy from 1903).
March, 1903, was an historic date for chemistry. It is, also, as we shall show, a date to which, in all probability, the men of the future will often refer as the veritable beginning of the larger powers and energies that they will control. It was in March, 1903, that Curie and Laborde announced the heat-emitting power of radium. [Robert Kennedy Duncan, "The New Knowledge," 1906]
Atomic bomb first recorded 1914 in writings of H.G. Wells ("The World Set Free"), who thought of it as a bomb "that would continue to explode indefinitely."
When you can drop just one atomic bomb and wipe out Paris or Berlin, war will have become monstrous and impossible. [S. Strunsky, Yale Review, January 1917]
Atomic Age is from 1945. Atomical "concerned with atoms," also "very minute," is from 1640s. Atomic clock is from 1938.