The term 'strong-arm' is a vivid compound formed from two native English words of Germanic origin. Literally describing a powerful limb, it employs the common metaphorical link between physical strength and coercive power. The concept likely emerged from the image of using brute force, as in grabbing or restraining someone. Over time, this concrete image evolved into an abstract adjective and verb describing any method of coercion that relies on threats or violence, not merely the literal use of an arm.

Structure: strong (powerful) + arm (limb) - strong: From Old English strang, meaning "powerful, mighty, severe." It is of Germanic origin, related to Dutch streng and German streng. In this compound, it functions as an adjective describing the nature of the force. - arm: From Old English earm, arm, meaning "the upper limb of the body." It is of Germanic origin, related to Dutch arm and German Arm. In this compound, it functions as a noun, metonymically representing physical power or violence.