dewlap n.

mid-14c., dewelappe, "fold of skin that hangs from the throat of oxen and cows," from lappe "loose piece" (Old English læppa), but the first element is of unknown origin or meaning and probably has been altered by folk-etymology. Old English had fræt-læppa in this sense (Middle English fresh-lappe), and compare Danish doglæp. Later applied to the fleshy fold or wattle of a turkey and also to the human throat when flaccid with age (1580s).