Where does “rhediadau” come from?

rhediadau (Welsh) comes from Welsh -au, from Middle Welsh -eu, from Old Welsh -ou, from Proto-Brythonic -ow, from Proto-Celtic -owes.

Ancestry of “rhediadau”, step by step

StepLanguageWordMeaning
1Welsh-au-s
2Middle Welsh-eu—
3Old Welsh-ou—
4Proto-Brythonic-ow—
5Proto-Celtic-owes—
Every word from Proto-Celtic -owes →Every word from Welsh -au →Every word from Middle Welsh -eu →