Where does “dau ddeg dwy” come from?

dau ddeg dwy (Welsh) comes from Welsh dwy, from Welsh dau, from Proto-Brythonic *dow, from Proto-Celtic *duwo, from Proto-Indo-European dwóh₁ — two.

Ancestry of “dau ddeg dwy”, step by step

dau ddeg dwy traces back through two separate lines of ancestry.

via Welsh dwy

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

via Welsh deg

StepLanguageWordMeaning
1Welshdegten; Soft mutation of teg
2Proto-Brythonicdegten
3Proto-Celticdekamten
4Proto-Indo-Europeandéḱm̥ten
Every word from Proto-Indo-European dwóh₁ →