An Etymological Dictionary of the German Language/Annotated/Eid
Eid, masculine, ‘oath, execration,’ from the equivalent Middle High German eit(d), Old High German eid, masculine; a word common to Teutonic, but not found in the other groups; Gothic aiþs, Old Icelandic eiðr, Anglo-Saxon âþ, English oath, Dutch eed, Old Saxon éth, masculine; for the common Teutonic aiþa-z, from pre-Teutonic ói-to-s (compare Old Irish oeth, ‘oath’), no suitable cognate has yet been found. Ehe and its cognates are scarcely allied to it, though Eidam may be so.