Green’s Dictionary of Slang

to go, esp. to run off.

1935		Thieves Slang ms list from District Police Training Centre, Ryton-on-Dunsmore, Warwicks 9: Scapa: Keep going.
1950		P. Hoskins No Hiding Place! 191/2: Scapa the Letty. Leave lodgings without paying .
1959		D. Niland Big Smoke 34: This is where I scapa.
2001		M. Coles Bible in Cockney 64: Then, the Spirit made him scapa into the desert.