Paris was originally a Roman city called 'Lutetia'

Lutetia was a town in preroman and Roman Gaul. The Gallo-Roman city was a predecessor of the re-made Merovingian town that is the ancesto...

Lutetia was a town in preroman and Roman Gaul. The Gallo-Roman city was a predecessor of the re-made Merovingian town that is the ancestor of present-day Paris.

Under Roman rule, Lutetia was altogether Romanised with a population of around 8,000. It didn't have a lot of political significance - the capital of its territory, Lugdunensis Senona, was Agedincum. It was Christianised in the 3rd century, generally when St Denis turned into the city's first bishop. The procedure was not at all peaceful – in around 250 A.D. St Denis and two associates were captured and decapitated on the hills of Mons Mercurius, where Roman foundations have been discovered, from that point of time it is known as Mons Martyrum. 

Lutetia was renamed Paris in 360 A.D., taking its name from the Gallic Parisii tribe name. The name had already been used for centuries as an adjective ("Parisiacus"). The legend of the Breton city of Ys recommends an alternate, if less likely, origin.