From an animal's snout to a gun's barrel — the muzzle metaphor compares a firearm to a metal beast with a projecting nose.
The projecting snout of an animal, or a guard placed over an animal's mouth, or the open end of a firearm barrel.
From Old French musel meaning snout or muzzle, diminutive of muse meaning snout or muzzle, from Medieval Latin musum meaning snout, of uncertain origin Key roots: musum (Medieval Latin: "snout").