bang v.

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.

The 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. Compare slang slap-up "excellent, first-rate" (by 1823).

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]