Smith is what's known as a polygenetic name (as opposed to a monogenetic one). A monogenetic one has a single origin, where all those who bear that name come from the same family; sometimes, we can reliably trace all the appearances of a surname to a particular region and find them all to be of one family tree. Smith is, on the other hand, found in thousands of medieval family heads in Britain who are unrelated.

Smith as a occupational name is linked to the Old English smið which is quite specifically for a worker in metal. Quoting Ælfric’s Colloquy from the 10th century:

Ic hæbbe smiþas (I have smiths), isene smiþas (iron smiths), goldsmiþ (gold smiths), seoloforsmiþ (a silversmith), arsmiþ (brass smiths)...

However, it's fairly tricky to derive the tempting conclusion that "smith" was later used as a generalized surname for all these designations; usually when used alone it was iron. Specific types of workers had their own name-linkages. For example, Gilder was the name for a goldsmith (derived from Old English gyldan). Bater (variant of Beater) could be a beater of metal, that is, a coppersmith. There were some names with the conjunction of the "smith" form, like Greensmith (being another variant for a coppersmith) but they weren't common enough to really account for the overwhelming abundance of Smiths, nor do we have evidence of serious cross-pollination. (It's not a force of zero -- when Smith started being popular someone could just shorten their name -- just it can't explain everything.)

The key here -- and this is based on the raw data, as opposed to guessing -- is that Smith is also a common locative name. That is, a smith is not just an occupation but a place you can go. It is given to people who lived near a blacksmith, or a town with a "Smith" variant (like Smeeth in Kent, which itself may have been named after a smith location). This type of naming is extremely common, and we also have some specific location variants like Smitham (from Smytham in Devon) which was given to

Robert de Smetham, 1275

Joan Smitham, 1562

Henrie Smytham, 1566

Peter Smytham, 1564

Alternatively, Smitheringale comes from Smither Gill, with (just as a sampling):

Thomas Smithergill, 1565

William Smigersgill, 1590

John Smythergill, 1594

Oliver Smithergale, 1632

Miller (variant of Milner) didn't quite have the same doubling; Mill was its own surname, like with Alexander Myll, who was a located at the grain mill of Kincrech in 1483.

The biggest competitor in occupational terms is Taylor/Tailor. It makes 6th in Archer's British Surname Atlas (45% the popularity of Smith), but it always had an uphill battle, because it was purely an occupational name. If the place a Tailor worked was also a Tailor with as much importance to the location as a place with a forge, there is a fair chance it would have made it to the top.

...

Hanks, P., Coates, R., & McClure, P. (Eds.). (2016). The Oxford Dictionary of Family Names in Britain and Ireland. Oxford University Press.

Stanley, E.G. Wonder-Smiths and Others: smið Compounds in Old English Poetry—With an Excursus on hleahtor. Neophilologus 101, 277–304 (2017).

Hello everyone,

If you are a first time visitor, welcome! This thread is trending high right now and getting a lot of attention, but it is important to remember those upvotes represent interest in the question itself, and it can often take time for a good answer to be written. The mission of /r/AskHistorians is to provide users with in-depth and comprehensive responses, and our rules are intended to facilitate that purpose. We remove comments which don't follow them for reasons including unfounded speculation, shallowness, and of course, inaccuracy. Making comments asking about the removed comments simply compounds this issue. So please, before you try your hand at posting, check out the rules, as we don't want to have to warn you further.

Of course, we know that it can be frustrating to come in here from your frontpage or /r/all and see only [removed], but we thank you for your patience. If you want to be reminded to come check back later, or simply find other great content to read while you wait, this thread provides a guide to a number of ways to do so, including the RemindMeBot- [Click Here to Subscribe](https://www.reddit.com/message/compose/?to=RemindMeBot&subject=Reminder&message=https://www.reddit.com/r/AskHistorians/comments/vkhkdm/why_is_smith_such_a_common_english_last_name_when/ RemindMe!++2+days) - or our Twitter.

Finally, while we always appreciate feedback, it is unfair to the OP to further derail this thread with META conversation, so if anyone has further questions or concerns, I would ask that they be directed to modmail, or a META thread. Thank you!