I've been just been looking at the 1859 Post Office Directory which lists all the commercial companies and traders in London.
My eye fell on the surname Mash. I note that of the eleven people listed with that name, no fewer than six were potato dealers (well, one of these was a greengrocer, so sold potatoes). Perhaps with that name they were drawn to the profession, like Thomas Crapper to toilet manufacture, or a former colleague of mine John Sparkes to electrical engineering.
I now plan to ask the curators to turn the directory open at the Bs, so I can check whether the theory holds good for people called Banger.
The directory is an exhibit in a very interesting exhibition of nineteenth century information design, Designing information before designers, organised by colleagues working on the AHRC funded project 'Designing information for everyday life, 1815-1914'. It has now moved from St Brides to Reading University where it will remain until 15 April.