1540s, "heavy, resounding blow;" see bang (v.). Meaning "loud, sudden explosive noise" is by 1855.
This is the way the world ends
Not with a bang but a whimper
[T.S. Eliot, from "Hollow Men," 1925]
1540s, "to strike hard with a loud blow," an imitative formation, or else from a Scandinavian source akin to Old Norse banga "to pound, hammer" also of echoic origin. Slang meaning "have sexual intercourse with" attested by 1937. As an adverb, "suddenly, abruptly," by 1828, probably from the notion of "with a sudden or violent sound." Related: Banged; banging. Banging (adj.) in the slang sense of "large, great, surpassing in size" is attested by 1864. Bang-up (adj.) "excellent, first-rate, in fine style" (1810) probably is shortened from a phrase such as bang up to the mark.
c. 1300, at first found chiefly in northern England and north Midlands writing, "powerful, strong," of obscure origin, possibly from a Scandinavian source (compare Norwegian dialectal bugge "great man"). Old English used micel (see much) in many of the same senses. It came into general use c. 1400. Meaning "of great size" is late 14c.; that of "full-grown, grown up" is attested from late 14c. Sense of "important, influential, powerful" is from c. 1400. Meaning "haughty, inflated with pride" is from 1570s. Meaning "generous" is U.S. colloquial by 1913.
Big band as a musical style is from 1926. Slang big head "conceit" is first recorded 1850. Big business "large commercial firms collectively" is from 1913 (before that it meant "a profitable income in business"). Big top "main tent of a circus" is from 1895. Big game "large animals hunted for sport" is from 1864. Big house "penitentiary" is U.S. underworld slang first attested 1915 (in London, "a workhouse," 1851). In financial journalism, big ticket items so called from 1956. Big lie is from Hitler's grosse Lüge.