Green’s Dictionary of Slang

1. (UK Und.) selling stolen property or even non-existent property to innocent purchasers who assume the goods are legitimate.

1925		E. Jervis 25 Years in Six Prisons 17: Some of the boys are ‘on the whiz’ (pickpockets), or ‘go screwing’ (burglars) or ‘telling the tale’ (confidence trick) or ‘tweedling.’.
1977		D. Powis Signs of Crime 206: Tweedling Selling stolen property, or selling non-existent property, or selling shoddy and worthless articles.
1989		J. Morton Lowspeak.

2. see tweedle, the n. (1)