From Middle English heron, heroun, heiron, from Anglo-Norman heiron, from Medieval Latin hairō, from Frankish and Proto-West Germanic *hraigrō, from Proto-Germanic *haigrô (compare Swedish häger and Danish hejre), dissimilation of *hraigrô (compare Old English hrāgra, Dutch reiger, German Reiher), from imitative Proto-Indo-European *(s)kreik-, *(s)kreig- (“to screech, creak”) (compare Welsh crëyr (“heron”), Ancient Greek κρίζω (krízō, “to creak, screech”). Compare also egret from the same Germanic etymon.