Where does “dau ddeg un” come from?

dau ddeg un (Welsh) comes from Welsh un, from Middle Welsh un, from Proto-Brythonic ʉn, from Proto-Celtic oinos, from Proto-Indo-European óynos — one; single.

dau ddeg un (Welsh): twenty-one

Definitions

  1. twenty-one

Ancestry of “dau ddeg un”, step by step

dau ddeg un traces back through 3 separate lines of ancestry.

via Welsh un

StepLanguageWordMeaning
1Welshunonly; one; one, individual
2Middle Welshunone
3Proto-Brythonicʉnone
4Proto-Celticoinosone
5Proto-Indo-Europeanóynosone; single

via Welsh dau

StepLanguageWordMeaning
1Welshdautwo
2Proto-Brythonic*dowtwo
3Proto-Celtic*duwotwo
4Proto-Indo-Europeandwóh₁two

via Welsh deg

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