Weapon

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Old English wǣp(e)n, of Germanic origin; related to Dutch wapen and German Waffe .

wiktionary

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From Middle English wepen, from Old English wǣpn, from Proto-Germanic *wēpną(“weapon”), of unknown origin, possibly from Proto-Indo-European *wēbnom. Cognate with Scots wapyn, wappen(“weapon”), West Frisian wapen(“weapon”), Dutch wapen(“weapon; coat of arms”), Low German wapen(“weapon”), German Waffe(“weapon”) and Wappen(“coat of arms”), Swedish vapen(“weapon”), Icelandic vopn(“weapon”).

etymonline

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weapon (n.)

Old English wæpen "instrument of fighting and defense, sword," also "penis," from Proto-Germanic *wēipna- (source also of Old Saxon wapan, Old Norse vapn, Danish vaaben, Old Frisian wepin, Middle Dutch wapen, Old High German wafan, German Waffe "weapon"), a word of unknown origin with no cognates outside Germanic; possibly a substratum word.