Where does “ēth” come from?

ēth (Old Frisian) comes from Proto-West Germanic aiþ, from Proto-Germanic aiþaz, from Proto-Indo-European oyt-.

Ancestry of “ēth”, step by step

StepLanguageWordMeaning
1Proto-West Germanicaiþoath
2Proto-Germanicaiþazoath
3Proto-Indo-Europeanoyt-—

Words derived from “ēth”

Every word from Proto-Indo-European oyt- →Every word from Proto-Germanic aiþaz →Every word from Proto-West Germanic aiþ →