mid-14c., from Old French aigrette, from Old Provençal aigreta, diminutive of aigron "heron," perhaps of Germanic origin (compare Old High German heigaro; see heron).
Entries linking to egret
heron n.
"long-necked, long-legged wading bird," c. 1300, from Old French hairon, eron (12c.), earlier hairo (11c., Modern French héron), from Frankish *haigiro or some other Germanic source, from Proto-Germanic *hraigran. Related to Old High German heigaro, Danish hejre "heron," German Reiher, Dutch reiger, Old Norse hegri), perhaps from a common IE root imitative of its cry (compare Old Church Slavonic kriku "cry, scream," Lithuanian krykšti "to shriek," Welsh cregyra "heron," Latin graculus "jackdaw, crow"). Old English cognate hraga did not survive into Middle English. Egret is from the same source.