Green’s Dictionary of Slang

Murphy (Game), the n.

[? orig. practitioners promised the victim a meeting with ‘a lovely woman called Mrs Murphy’. The murphy can be extended to drug ‘deals’ and other illicit commerce]

1. [1950s+] (orig. US Und.) of a prostitute, luring a client either to a room or a deserted alley, hallway etc. and then, instead of having sex, the client is beaten and robbed by a male accomplice, who may just strike, but may also pose as an aggrieved father, lover, brother etc; also attrib.

2. [1960s+] (US) a swindle in general.

In compounds

Murphy man (n.)

[1960s+] a man who specializes in the Murphy game.