whewer

Century, Wright's English Dialect Dictionary and the 1933 OED take it to be from whew (“(to make) a shrill whistling sound like the cry of a plover”) +‎ -er, and early cites also call the bird the "whistling widgeon".

• (non-rhotic) IPA^(key): /hwjuːə/; (without the wine–whine merger) IPA^(key): /ʍjuːə/
• (rhotic) IPA^(key): /hwjuːɚ/; (without the wine–whine merger) IPA^(key): /ʍjuːɚ/

whewer (plural whewers)

1. (UK, dialect) whew duck, Eurasian wigeon, wigeon (Mareca penelope).
   • 1634, Althorp MS. in Simpkinson, Washingtons (1860), page xxiii:

     Peckards 3—broadbills 5—whewers 2

   • 1668, Charleton, Onomast., page 100:

     Boscas, aliis Anas Fistularis [...] the Whewer, or Whistling Widgeon.

   • 1718 [1674], John Ray, Francis Willughby, Philosophical Letters Between the Late Learned Mr. Ray and Several of His Ingenious Correspondents, Natives and Foreigners: To which are Added Those of Francis Willughby Esq, page 21:

     With the Fish I have put up in a Box some Water Fowl, viz. a Pocker, a Smew, three Sheldins, a Widgeon, and a Whewer; which two last are Male and Female of the same kind.

   • 1806, Thomas Smith, The Naturalist's Cabinet: Containing Interesting Sketches of Natural History; Illustrative of the Natures, Dispositions, Manners, and Habits of All the Most Remarkable Quadrupeds, Birds, Fishes, Amphibia, Reptiles, &c. in the Known World, page 217:

     Widgeons are common in Cambridgeshire, the Isle of Ely, &c. where the male is called the widgeon, and the female, the whewer. They feed upon wild periwinkles, grass, weeds, &c. which grow at the bottom of rivers and lakes. Their flesh has a very delicious taste, not inferior to teal, or wild ducks.

   • 1908, Illustrated Sporting & Dramatic News, page 172:

     the choicer fowl of mallard and widgeon (locally "whewers"), both in the Humber and the Tees, the former species being, of course, resident in the county.

• “whewer”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.
• “whewer”, in The Century Dictionary […], New York, N.Y.: The Century Co., 1911, →OCLC.
• Oxford English Dictionary, 1884–1928, and First Supplement, 1933.
• Joseph Wright, editor (1905), “WHEW”, in The English Dialect Dictionary: […], volumes VI (T–Z, Supplement, Bibliography and Grammar), London: Henry Frowde, […], publisher to the English Dialect Society, […]; New York, N.Y.: G. P. Putnam’s Sons, →OCLC.