means A shot is a small discrete burst of action — a firing of a gun, an attempt at something, a measured swallow of liquor, or a single image captured — depending entirely on what you're aiming at.

from From Old English 'sceot' or 'scot,' meaning the act of shooting, tied to the verb 'shoot' (Old English 'sceotan,' to move swiftly or launch a missile). The root runs back through Proto-Germanic '*skeutan' and is a cousin of words like 'scoot' and 'sheet.' The drinking sense — a quick measured pour — and the photographic sense both lean on that core idea of a single swift discharge: something released all at once, then gone.