1911 Encyclopædia Britannica/Dewlap

DEWLAP (from the O.E. læppa, a lappet, or hanging fold; the first syllable is of doubtful origin and the popular explanation that the word means “the fold which brushes the dew” is not borne out, according to the New English Dictionary, by the equivalent words such as the Danish doglaeb, in Scandinavian languages), the loose fold of skin hanging from the neck of cattle, also applied to similar folds in the necks of other animals and fowls, as the dog, turkey, &c. The American practice of branding cattle by making a cut in the neck is known as a “dewlap brand.” The skin of the neck in human beings often becomes pendulous with age, and is sometimes referred to humorously by the same name.