1650s, "active operation;" 1670s, "a mode of exerting power or producing effect," from Medieval Latin agentia, abstract noun from Latin agentem (nominative agens) "effective, powerful," present participle of agere "to set in motion, drive forward; to do, perform," figuratively "incite to action; keep in movement" (from PIE root *ag- "to drive, draw out or forth, move"). The meaning "establishment where business is done for another" is recorded by 1861.
Proto-Indo-European root meaning "to drive, draw out or forth, move."
It forms all or part of: act; action; active; actor; actual; actuary; actuate; agency; agenda; agent; agile; agitation; agony; ambagious; ambassador; ambiguous; anagogical; antagonize; apagoge; assay; Auriga; auto-da-fe; axiom; cache; castigate; coagulate; cogent; cogitation; counteract; demagogue; embassy; epact; essay; exact; exacta; examine; exigency; exiguous; fumigation; glucagon; hypnagogic; interact; intransigent; isagoge; litigate; litigation; mitigate; mystagogue; navigate; objurgate; pedagogue; plutogogue; prodigal; protagonist; purge; react; redact; retroactive; squat; strategy; synagogue; transact; transaction; variegate.
It is the hypothetical source of/evidence for its existence is provided by: Greek agein "to lead, guide, drive, carry off," agon "assembly, contest in the games," agōgos "leader," axios "worth, worthy, weighing as much;" Sanskrit ajati "drives," ajirah "moving, active;" Latin actus "a doing; a driving, impulse, a setting in motion; a part in a play;" agere "to set in motion, drive, drive forward," hence "to do, perform," agilis "nimble, quick;" Old Norse aka "to drive;" Middle Irish ag "battle."
U.S. civilian espionage agency, initialism (acronym) of Central Intelligence Agency, founded 1947 as successor to the Office of Strategic Services (OSS).
official news agency of the former U.S.S.R., formed in 1925, an acronym of Russian T'el'egrafnoye ag'enstvo Sov'etskovo Soyuza "Telegraphic Agency of the Soviet Union."
initialism (acronym) for Environmental Protection Agency, U.S. federal agency proposed by President Richard Nixon and created in December 1970.
U.S. space agency, acronym of National Aeronautics and Space Administration, set up in 1958.
1936, initialism (acronym) from Works Progress Administration, U.S. agency established 1935.
in reference to a semi-official detective, 1888 (Pinkerton men), from the detective agency begun in U.S. 1850 by Allan Pinkerton (1819-1884).
national security agency of the Soviet Union from 1954 to 1991, attested from 1955 in English, initialism (acronym) of Russian Komitet gosudarstvennoy bezopasnosti "Committee for State Security."
