the.com/machine gun

A firearm that fires bullets continuously and rapidly while the trigger is held, designed for sustained lethal force.

means An automatic firearm that fires bullets continuously and rapidly for as long as the trigger is held and ammunition feeds through.

from Straightforward compound — 'machine' + 'gun' — coined in the 1800s as inventors built weapons that mechanized the loading and firing cycle once done by hand. Early tries like the hand-cranked Gatling gun of the 1860s paved the way, but the term 'machine gun' properly took hold with truly automatic designs like Hiram Maxim's 1880s gun, which used the force of its own recoil to eject, reload, and fire again without the shooter cranking anything. The name just describes the thing plainly: a gun that runs like a machine.

origin
Gatling gun, 1861, intended to reduce army size
irony
Invented partly hoping it would make war less deadly
defining trait
Reloads itself using the gun's own recoil or gas
linguistic drift
Now slang for anything rapid and relentless, like talking
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