A soldier who, as the term is, sings out at the halberts. It is a point of honour in some regiments, among the grenadiers, never to cry out, become nightingales, whilst under the discipline of the cat of nine tails; to avoid which, they chew a bullet.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Night Magistrate * NightmanNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes