Where does “dydd Iau” come from?

dydd Iau (Welsh) comes from Welsh dydd, from Middle Welsh dyð, from Old Welsh did, from Proto-Brythonic dið, from Proto-Celtic dīyos, from Proto-Indo-European dyḗws, from Proto-Indo-European dyéws, from Proto-Indo-European dyew- — to be bright; sky, heaven.

dydd Iau (Welsh): Thursday

Definitions

  1. Thursday

Ancestry of “dydd Iau”, step by step

dydd Iau traces back through 3 separate lines of ancestry.

via Welsh dydd

StepLanguageWordMeaning
1Welshdyddday, daytime
2Middle Welshdyðday
3Old Welshdidday
4Proto-Brythonicdiðday, daytime
5Proto-Celticdīyosday
6Proto-Indo-Europeandyḗwssky, heaven; sky god
7Proto-Indo-Europeandyéwssky, heaven
8Proto-Indo-Europeandyew-to be bright; sky, heaven

via Welsh Iau

StepLanguageWordMeaning
1WelshIauJupiter, Thursday
2Middle Welshieu
3Brythonic*Yow
4LatinIovem

via Latin dies iovis

StepLanguageWordMeaning
1Latindies iovisThursday
2LatindiēsA day, particularly
3Proto-Italicdjēmaccusative singular of *djous
4Proto-Italic*djous
Every word from Proto-Indo-European dyew-Every word from Proto-Indo-European dyéwsEvery word from Proto-Indo-European dyḗws