Etymograph > Indo-European > Old English > Dictionary > ǣdre

river; vein, artery; nerve, sinew; kidney

Source: Kroonen 2013:120
originates from: PGmc *ēþrō- "vein, rivulet" (ēþrō- > āþrō > āþrū > āþru > ǣþru > ǣþr > ǣþer) through pgmc-to-oe
(source: Kroonen 2013:120)