A link-boy: link-boys are said to curse the moon, because it renders their assistance unnecessary; these gentry frequently, under colour of lighting passengers over kennels, or through dark passages, assist in robbing them. Cant.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Monosyllable * Moon-eyed HenNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes