Where does “ēþ” come from?

ēþ (Old Danish) comes from Old Norse eiðr, from Proto-Germanic aiþaz, from Proto-Indo-European oyt-.

Ancestry of “ēþ”, step by step

StepLanguageWordMeaning
1Old Norseeiðroath
2Proto-Germanicaiþazoath
3Proto-Indo-Europeanoyt-—
Every word from Proto-Indo-European oyt- →Every word from Proto-Germanic aiþaz →Every word from Old Norse eiðr →