From Old Englishǣdre(“a vein, artery; sinew”), from Proto-Indo-European*ēt-er-(“stomach, intestines”). Cognates include (from Germanic) Old Saxon -āðara (Dutch ader), Old High German ādra (German Ader), Old Norse æðr (Swedish åder); (from Indo-European) Ancient Greek ἦτορ(êtor, “heart”), Latin uterus, Old Irish inathar(“entrails”).