I have AJP Crown to thank for this link: “Surnames of Occupation,” by C.M. Matthews (from History Today 13: 1963). It begins “Modern English surnames are so many fragments of medieval conversation, crystallized into permanent form,” and is full of interesting tidbits. A couple of excerpts:
Naturally, we must begin with Smith, the commonest English surname of any type. Among occupational names, it is in a class by itself with 5,750 examples, more than twice as many as any other. The reason for this multiplicity is not so much that metal-workers were numerous as that they were important and widespread. On the skill of the smith, both rich and poor depended for the most essential things of life, the tools of husbandry and the weapons of hunting and war. Every community in the land must have one, every castle, every manor; and so distinctive was his trade that he would seldom need another name.
Everyone knows that Smith comes first; but probably not many could name the second among names of occupation. Two names run very close together, Clark and Taylor, the former being slightly ahead with 2,740 as against 2,570. It is not at all surprising that the clerk should be so high on the list. Like the smith, he had a skill that was needed everywhere and rare enough to be valued—literacy. [...]
It is natural that there should have been a miller in every village, and that, like the smith, he should take his name from his trade. Its numbers are harder to assess than some, because it has survived in various forms: Milner, the Early Middle English form which generally developed into Miller, and—with exactly the same meaning—Millward or Millard. These names taken together amount to 1,710.
But, besides these, there are 780 more closely connected with the building from which the trade was inseparable. Anglo-Saxon “mylen” gives us Milne, Mill and, even more commonly, Mills (the final “s” attached to many common names remains a puzzle to the experts). Many of these names must have referred to the miller himself, but some to his servants or merely to people who lived at or near the mill. If we add all these, the milling business would nearly equal the tailoring, but still remain in fourth place on our list.
I hadn’t realized that final -s in names was a mystery, but now that I think of it it’s certainly not clear where it would come from.