köken: From Middle High German zweinzec, from Old High German zweinzug, from Proto-Germanic *twaintigaz, *twai tigiwiz. Cognate with Dutch twintig, West Frisian tweintich, English twenty, Danish tyve. The form zwanzig goes back to dialects that had early on lowered Middle High German -ei- to [aɪ̯] (especially Bavarian); elsewhere the contraction yielded zwenzig, which waned around 1700 along with the…
köken: From Proto-Turkic *yẹgirmi (“twenty”). Cognate with Old Turkic 𐰘𐰏𐰼𐰢𐰃 (y²gr²mi), Azerbaijani iyirmi, Bashkir, Tatar егерме (yegerme), Kyrgyz жыйырма (jıyırma), Turkish yirmi, Uyghur يىگىرمە (yigirme), Uzbek yigirma, etc.
köken: Inherited from Volga Bulgar جيرم (ciyermi), from Proto-Turkic *yẹgirmi. Cognate with Khalaj yigirmi, Turkish yirmi, Uzbek yigirma, Bashkir егерме (yegerme), and Yakut сүүрбэ (süürbe).
köken: Believed to be cognate with 果(は)て (hate, “end”), with 20 signifying the "limit" of one person's counting ability using two feet and two hands. Already in declining use by the Heian period in favour of 二十(にじゅう) (nijū). Note also Ainu ホッ (hot, “twenty”).
Inherited from Middle French vingt, from Old French vint, from Latin vīgintī, from Proto-Indo-European *h₁wih₁ḱm̥ti, *dwi(h₁)dḱm̥ti. The Latin -g- was regularly lost in Old French, but was added back to the spelling in Middle French (now placed after the -n- in order to maintain the pronunciation).