ˈad.ər noun
( -s )
Etymology: Middle English, from Old English ātor; akin to Old High German eitar poison, Old Saxon ettar, Old Norse eitr, Old High German eiz pustule, boil, Greek oidos swelling, tumor, Old Slavic jadŭ poison, and perhaps to Sanskrit indra- strong, and perhaps to Old English āte oat
chiefly Scotland : corrupt matter from a sore