Whew \Whew\ (hw[=u]), n. & interj. A sound like a half-formed whistle, expressing astonishment, scorn, or dislike.
Whew duck, the European widgeon. [Prov. Eng.]
Source: Webster's Revised Unabridged Dictionary (1913)
Whew \Whew\, v. i. To whistle with a shrill pipe, like a plover. [Prov. Eng. & Scot.]