And here's an intersting look at the general etymological gestation of British surnames (get a load of what Dickens actually means! )...and, to the Davids among us, look at all the derivations "David" spawned):

http://www.familychronicle.com/british.htm

And it has this to say about occupational names:

>OCCUPATIONS

Occupational surnames are self-explanatory: Barber, Plumber, Baker, etc. Some apparently obvious occupational names aren't what they may seem, however. A Farmer did not work in agriculture but collected taxes, and Banker is not an occupational surname at all, meaning "dweller on a hillside".<