An Etymological Dictionary of the German Language/Annotated/zwanzig

by Friedrich Kluge

zwanzig, numeral, ‘twenty,’ from the equivalent Middle High German zweinzec, zwênzic, Old High German zweinzug; a common West Teutonic numeral. Compare Old Saxon twêntig, Low German and Dutch twintig, Old Frisian twintich, Anglo-Saxon twêntig (from twœ̂gentig?), English twenty (see -zig). The n of the first component seems to be a mark of the nominative plural masculine, as in Old High German zwên-e, Anglo-Saxon twêgen; see zwei.