Where does “ooth” come from?

ooth (Middle English) comes from Old English āþ, from Proto-West Germanic aiþ, from Proto-Germanic aiþaz, from Proto-Indo-European oyt-.

Ancestry of “ooth”, step by step

StepLanguageWordMeaning
1Old Englishāþoath
2Proto-West Germanicaiþoath
3Proto-Germanicaiþazoath
4Proto-Indo-Europeanoyt-—

Words derived from “ooth”

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