firearm (n.)youdaoicibaDictYouDict[firearm 词源字典]
also fire-arm, 1640s, from fire (n.) + arm (n.2). Anything which expels a missile by combustion of gunpowder (or a similar substance), from a pistol to a cannon. Related: Firearms.[firearm etymology, firearm origin, 英语词源]
forearm (n.)youdaoicibaDictYouDict
between the elbow and the wrist, 1741, from fore- + arm (n.1).
forearm (v.)youdaoicibaDictYouDict
"prepare for an attack," 1590s, from fore- + arm (v.) "take up weapons." Related: Forearmed; forearming.