Original Latin names of Spanish, French, and Italian towns and regions

Factual Questions
1

Does anyone know of an online list anywhere that explains, fairly comprehesively, how the names of towns and regions in Romance-language countries developed from Latin? Some major examples are fairly well known, like: [ul][li]Londinium=>London[]Caesar Augustus=>Saragossa[]Bonnonia=>BolognaBarium=>Bari[/ul][/li]
But what of smaller towns? For example, it occurred to me that many French towns seem to end in /-s/, such as Lyons, Arles, and Nimes. Did this /s/ usually come from a plural ending, or was it from a nominative singular declension in /us/?

And what of Romanian names like Ploest?

2

Ploesti was founded in the 16th century, so as far as I know, it never had a Latin name. Arles comes from the Celtic name of the town, Arlate. Lyon comes from the Celtic name of the town, also, “Lugdunum” Nimes apparenly was once “Nemausus”.

3

Orbis Latinis, which also links to BSC Latin Place Names File and Names of Printing Towns. Those three sites should have most cities with Latin equivalents.

4

Lyons doesn’t get a final “s” in french. Marseilles doesn’t, either. I wouldn’t know why these were added in english (original names of these towns : Lugdunum an Massilia).
The latin name of Arles was Arelate. I’ve no clue why it got an “s” (this times, the spelling is identical in french).

I can’t remember the latin name of Nimes, but I’m quite certain it was a longer name actually including a “s” (Something like, say, Nemausis) and probably lost its final syllabe.

For the record, Paris is named after the celtic tribe living in this area, the Parisii, so in this case too the final syllabe was dropped, but the “s” kept. Paris got its name only during the late roman empire, or maybe after the fall of the empire, I don’t remember. It’s original name was Lutetia (Maybe a celtic name, but I don’t remember, either).

Something of interest re. your OP : the same thing happened to a number of large french towns that originally were the main town of a particular celtic people/tribe. They lost their original name which was replaced by a derivation of the name of this people. These new names (often? always?) got a final “s”. Reims, Troyes, Limoges, Chartres are some examples, but I know there are many more. So, it might be that the name of most towns you could wonder about (probably large towns if you’re aware of their existence) followed this pattern.

5

thanks, these are exactly what I was looking for!