Forearm

wiktionary

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From fore- +‎ arm. Compare Dutch voorarm(“forearm”), Danish forarm(“forearm”), German Vorderarm(“forearm”).

etymonline

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forearm (n.)

between the elbow and the wrist, 1741, from fore- + arm (n.1).

forearm (v.)

"prepare for an attack," 1590s, from fore- + arm (v.) "take up weapons." Related: Forearmed; forearming.