Where does “ddwyfed ar hugain” come from?

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

Ancestry of “ddwyfed ar hugain”, step by step

StepLanguageWordMeaning
1Welshdwyfeminine of dau; two
2Welshdautwo
3Proto-Brythonic*dowtwo
4Proto-Celtic*duwotwo
5Proto-Indo-Europeandwóh₁two
Every word from Proto-Indo-European dwóh₁ →