Green’s Dictionary of Slang

a door-to-door salesman.

[1895		Mirror of Life 20 July 6/1: Harry has the finest fish that swim, and he pats his salmon or his Dutch plaice as affectionately as if they were his children, and says a ‘mossel brocker’ (a benediction over them)].
1960		J. Franklyn Dict. of Rhy. Sl.
1969		S.T. Kendall Up the Frog.
1992		R. Puxley Cockney Rabbit.