nicker (v.)

Middle English neighen, from Old English hnægan "to neigh, utter the cry of a horse," probably of imitative origin (compare Old Norse gneggja "to neigh," Middle High German negen, French hennir, Japanese inanaki). In Middle English also nyghe, neyen, nyen, nayʒen. Related: Neighed; neighing. As a noun, "the cry of a horse, a whinnying," from 1510s.