Paris was known by the Romans as Lutetia or Lutetia Parisorium, but was later shortened to just Paris. Celtic legend prefers to ascribe the name "Paris" to "par Ys", in reference to the "lost city" of Ys, in the Bay of Douarnenez in Brittany. With the loss of Ys, Lutetia was the only other city which could compare, and became known as like Ys.
In 508 Clovis made Paris, with an estimated population of 30,000, the capital of his Merovingian empire. In the 9th century Paris began to feel pressure from Viking raiders, and in 845 the city was sacked.
In the 12th century the University of Paris was founded, one of the oldest in Europe. By the early 14th century Paris had grown to a population of 250,000. However the black death decimated Paris, and it was not to reach that population again until the 16th century.