Green’s Dictionary of Slang

1. money.

1844

W.H. Oxberry Oxberry's Budget of Plays 108/2: But all was set right by a snip,— / ‘His purse is superfine,’ / Said he, ‘And he has lots of flip, / Though he wears a four and nine’.

2. a bribe or tip.

1934		P. Allingham Cheapjack 318: Flip – A racing tip.
1937–84		Partridge DSUE (1984) 407/1: C.19–20.