Green’s Dictionary of Slang

slip n.²

the back pocket of a tail-coat.

1812		Vaux Vocab. of the Flash Lang.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.

SE in slang uses

In phrases

give someone the slip (v.) [SE give the slip, to elude, to run off]

to die.

1906

W. Boyle Eloquent Dempsy (1911) Act I: He was so near to giving us the slip three days ago.