Meaning

noun a hanging fold of loose skin on an elderly person's neck

originFrom Middle English dewlappe. The first element may be dew (and if not, seems to have been altered by folk etymology to resemble it); the second element is lap (“loose fabric”), Old English læppa (“a loose hanging piece”); compare jellop and jowlop (from jowl + lap), and dewclaw. Compare old Norwegian and Danish doglæp (the modern Danish word for "dew" is dug, but compare Old Norse dǫgg (“dew”)…

Etymology from Wiktionary, CC BY-SA 3.0