SNUG,
All's snug; All's quiet, used by Villains, when every thing is silent and they hear no body stir to oppose their intended Rogueries.
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Entry taken from 1736 Canting Dictionary, by Nathan Bailey.
Snug in the 1811 Vulgar Tongue
Also see examples in Canting Songs and Slang Rhymes collected by John S. Farmer (1896).