To RUB,
to run away. A Rub, an Impediment, Obstacle, Hinderance, Stop, Hardship, or Difficulty. Rub on, to live indifferently. Rub through the World, to live tolerably well in it.
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Entry taken from 1736 Canting Dictionary, by Nathan Bailey.
To Rub in the 1811 Vulgar Tongue
Also see examples in Canting Songs and Slang Rhymes collected by John S. Farmer (1896).