تعريف ومعنى "knuckle sandwich"

What is the origin of the idiom "knuckle sandwich" and when to use it?

The idiom "knuckle sandwich" originated in the early 20th century as slang for a punch to the face or a physical blow, often in the form of a fist to the mouth or nose. The phrase is a playful way of describing a violent action and is meant to sound more lighthearted than a real threat, despite its aggressive undertones.