Where does “reyth” come from?

reyth (Middle Welsh) comes from Proto-Brythonic rreiθ, from Proto-Celtic rextus, from Proto-Indo-European h₃reǵ-tus.

Ancestry of “reyth”, step by step

StepLanguageWordMeaning
1Proto-Brythonicrreiθrule, law
2Proto-Celticrextusrule, law; fury, anger
3Proto-Indo-Europeanh₃reǵ-tus—

Words derived from “reyth”

Every word from Proto-Indo-European h₃reǵ-tus →Every word from Proto-Celtic rextus →Every word from Proto-Brythonic rreiθ →
reyth — Etymology, Origin & Word History | Etymology Explorer