Many thanks again for so much useful advice. I like Fred Hoffman's suggestion that "surnames tend to come from concrete, familiar, everyday things". I am reminded, in particular, of one of my Flemish friends, called Bruynooghe, who true to his name has deep brown eyes, and of a French friend, Roussel, who has brilliant red hair, both no doubt inherited from a distant ancestor. I suspect that people with the surname Smith or Kowalski are, like me, bigger than other people on the average, because it goes with the job!