Where does “ugain namyn dwy” come from?

ugain namyn dwy (Welsh) comes from Welsh ugain, from Old Welsh uceint, from Proto-Brythonic ʉgėnt, from Proto-Celtic wikantī, from Proto-Indo-European h₁wih₁ḱm̥t, from Proto-Indo-European dwi(h₁)dḱm̥ti — two tens; two decades; twenty; two-ten.

Ancestry of “ugain namyn dwy”, step by step

ugain namyn dwy traces back through 3 separate lines of ancestry.

via Welsh ugain

StepLanguageWordMeaning
1Welshugaintwenty; score
2Old Welshuceint—
3Proto-Brythonicʉgėnt—
4Proto-Celticwikantītwenty
5Proto-Indo-Europeanh₁wih₁ḱm̥t—
6Proto-Indo-Europeandwi(h₁)dḱm̥titwo tens; two decades; twenty; two-ten

via Welsh dwy

StepLanguageWordMeaning
1Welshdwyfeminine of dau; two
2Welshdautwo
3Proto-Brythonic*dowtwo
4Proto-Celtic*duwotwo
5Proto-Indo-Europeandwóh₁two

via Welsh namyn

StepLanguageWordMeaning
1Welshnamynexcept, apart from
Every word from Proto-Indo-European dwi(h₁)dḱm̥ti →
ugain namyn dwy — Etymology, Origin & Word History | Etymology Explorer