minder noun a criminal’s bodyguard or enforcer UK,1924 Made very familiar to the UK public with the television series Minder, 1979–94.
[T]he penman, who never drops [passed forged cheques] himself, has to send a minder, known as a topper, to keep an eye on the dropper, make sure he doesn’t pocket the crinkle [money][.] — Charles Raven, UnderworldNights, p. 81, 1956