The tenth order of the canting tribe, who not only rob, but beat, and often murder passenges. Cant. Swaddlers is also the Irish name for methodist.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
See also the definition in Nathan Bailey's 1736 dictionary of canting and thieving slang.
To Swaddle * SwagNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes