The compound adjective and verb 'stiff-armed' is a transparent formation from native English elements. The first element, 'stiff', carries its ancient Germanic sense of being unbending and rigid. The second element, 'arm', refers directly to the physical limb. When combined with the suffix '-ed', which here functions to form a participial adjective, the term literally describes the state or action of having a rigidly straight arm. This literal image evolved into the specific sporting and colloquial sense of pushing away an opponent or obstacle with force, leveraging the straight arm as a tool of extension and rejection, most famously associated with a move in American football.

Structure: stiff (rigid) + arm (limb) + ed (adjective/verb suffix) - stiff: From Old English stīf, meaning rigid, not easily bent. Germanic origin. - arm: From Old English earm, meaning the upper limb of the body. Proto-Germanic origin. - ed: A suffix used to form adjectives from nouns (e.g., 'talented') or to indicate the past tense and past participle of verbs. Old English origin.