Green’s Dictionary of Slang

gossip n.

SE in slang uses

In phrases

up to someone’s gossip (adj.)

aware of what is going on, shrewd, experienced.

1781		G. Parker View of Society II 80: This trick had been once attempted upon a landlord who was a man of the world, and up to their gossip.
1785		Grose Classical Dict. of the Vulgar Tongue n.p.: Up to their gossip. To be a match for one who attempts to cheat or deceive; to be on a footing, or in the secret.
1859		Hotten Dict. of Modern Sl. etc. 113: UP TO ONE’S GOSSIP, to be a match for a person who attempts to cheat or deceive.
1860		Hotten Dict. of Modern Sl. etc. [as cit. 1859].