Wiltshire men: because it is said that some men of that county, seeing the reflection of the moon in a pond, endeavoured to pull it out with a rake.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Moon Men * MoonshineNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes