Lots of families here trace their heritage to towns in Europe that are the same as the family name. Which usually came first - the family name or the town’s name? I believe that last names often derived from the town of origin, e.g. Leonardo *from Vinci. * But towns were also named for the families that were most prominent there. What is most common, family name or town name first?
People were named after places, generally.
However, there are here a lot of places named after the owner of a Gallo-Roman villa (most names ending in -ac in western France, in -y in northern France). A significant part of French villages originated in such villae. That’s probably the major source of places named after people in France, even though such names aren’t readily recognizable. It’s not obvious that Roissy airport is ultimately named after some Roman guy called Rossius. Apart from that, places are way more commonly called after geographic features than after people.
For the Germanic-language area it seems to have gone two ways:
Early Middle Age and earlier - First name to town name: German and Austrian town names ending in -ing, -ingen, -ingheim and some other suffixes are thought to be derived from the name of a chief or head of family settling there. This also applies to other Germanic peoples (e.g. Nottingham from one Snot, Birmingham from one Beorma, Langobardic foundations in Northern Italy ending in -engo)
Later, when family names were adopted (since about the 12th c.): a last name ending in -inger usually derives from a place ending in -ing, also some last names ending in -er deriving from a toponym to which the -er was appended.
In England there is a wide variety of sources for names. Many are Roman, Norman or Saxon in origin. Places ending in caster/cester/caister/chester come from the Latin word *castra *or Saxon ceaster, meaning a camp or settlement. Burh or burgh meant a fort or fortified place. There are dozens of them.
Spellings are pretty arbitrary - When the earliest records began, like the Domesday Book, the person writing the name simply made it up. When people started to make proper maps, they would ask someone “What’s this place called?” You can imagine that many people would not know - “It’s the village,” they might say, in an incomprehensible accent. So the map makers often had to improvise and we have whole groups of villages like Nether, Middle and Over Wallop. (Nether Wallop doubled up as St. Mary Mead for any followers of Miss Marple)
The nobility took their names from places - Lancaster and York for example. (York is from the Viking Jorvik)
Which towns are you thinking of that are named after a family?
I think for place names in general this is not a question that’s answerable. There are tens of thousands of family names based on places and tens and thousands of place names based on a persons name.
A town in England might be named, say, Massingham, after the founder Massa: subsequent people living there could take Massingham as their surname.
There would be very little connection between these families and Massa, who had been in the cold, cold ground for 600 years when Jehan de Massingham left the village in 1300 and founded a long line of accountants.
Washington’s an fun instance: George Washington’s family took their name from Washington in North East England, which was most likely named for someone named Hwæsa (or something like it).
So Washington DC is a place named after a person named after a place named after a person.
Saint’s names are popular: St Albans, St Andrews, St Davids for example. Some more modern ones like Telford (Thomas Telford) and Peterlee (Peter Lee, a miners’ leader).
Fort William in Scotland was named after William Of Orange, but renamed several times (William was not universally popular) before being named Fort William again, this time after Prince William, Duke of Cumberland.