Act comes straight from Latin, and its shape shows it. Latin had actus, "a doing, a driving, a part in a play," and actum, "a thing done" — both from agere, "to set in motion, drive forward," hence "to do." That -ct- cluster in the middle is a very Latin sequence of sounds, and English took it over intact rather than softening it the way French often did. Short, blunt, and consonant-heavy though it looks, act is a borrowing, not a native word.
It entered English in the late 1300s meaning simply "a thing done." The theatrical sense — a part of a play — and the legal and legislative senses were already there in Latin, so English got them as part of the package rather than inventing them. Later additions are all English: an act in a variety show is from 1890, an act meaning put-on behaviour from 1928, and getting your act together only from the 1970s.
act
(n.)
late 14c., "a thing done," from Latin
actus
"a doing; a driving, impulse, a setting in motion; a part in a play," and
actum
"a thing done" (originally a legal term), both from
agere
"to set in motion, drive, drive forward," hence "to do, perform," figuratively "incite to action; keep in movement, stir up" (from PIE root
*ag-
"to drive, draw out or forth, move").
The verb
agere
had a broad range of meaning in Latin, including "act on stage, play the part of; plead a cause at law; chase; carry off, steal." The theatrical ("part of a play," 1510s) and legislative (early 15c.) senses of the noun also were in Latin.
The meaning "one of a series of performances in a variety show" is from 1890. The meaning "display of exaggerated behavior" is from 1928, extended from the theatrical sense.
In the act
"in the process" is from 1590s, perhaps originally from a late 16c. sense of
the act
as "sexual intercourse."
Act of God
"uncontrollable natural force" is recorded by 1726.
An act of God is an accident which arises from a cause which operates without interference or aid from man (1 Pars. on Cont. 635); the loss arising wherefrom cannot be guarded against by the ordinary exertions of human skill and prudence so as to prevent its effect. [William Wait, "General Principles of the Law," Albany, 1879]
To
get into the act
"participate" is from 1947; to
get (one's) act together
"organize one's (disorderly) life" is by 1976, perhaps euphemistic.
also from late 14c.
act
(v.)
mid-15c.,
acten
, "to act upon or adjudicate" a legal case, from Latin
actus
, past participle of
agere
"to set in motion, drive, drive forward," hence "to do, perform," also "act on stage, play the part of; plead a cause at law" (from PIE root
*ag-
"to drive, draw out or forth, move").
The verb is original in Latin, but most of the modern verbal senses in English probably are from the noun. The general sense of "to do, perform, transact" is from c. 1600. Of things, "do something, exert energy or force," by 1751. In theater use from 1590s as "perform as an actor" (intransitive), 1610s as "represent by performance on the stage" (transitive). The general meaning "perform specific duties or functions," often on a temporary basis, is by 1804.
To
act on
"exert influence on" is from 1810. To
act up
"be unruly" is by 1900 (in reference to a horse). Earlier it meant "acting in accordance with" a duty, expectation, or belief (1640s). To
act out
"behave anti-socially" (1974) is from psychiatric sense of "expressing one's unconscious impulses or desires" (
acting out
is from 1945). Related:
Acted
;
acting
.
also from mid-15c.
act came in through Latin, and its spelling follows that family's conventions.
How that family writes these sounds
| /kt/ | -ct-, a cluster Latin tolerated and English inherited wholeact, fact, direct, instinct |
What gives it away on the page
| -ct- | A cluster Latin tolerated and English inherited wholesale.act, fact, direct, instinct |