The origin of the name, Pisa, is a mystery. While the origin of the city had remained unknown for centuries, the Pelasgi, the Greeks, the Etruscans, and the Ligurians had variously been proposed as founders of the city (for example, a colony of the ancient city of Pisa, Greece). Archaeological remains from the 5th century BC confirmed the existence of a city at the sea, trading with Greeks and Gauls. The presence of an Etruscan necropolis, discovered during excavations in the Arena Garibaldi in 1991, confirmed its Etruscan origins.
Ancient Roman authors referred to Pisa as an old city. Strabo referred Pisa's origins to the mythical Nestor, king of Pylos, after the fall of Troy. Virgil, in his Aeneid, states that Pisa was already a great center by the times described; the settlers from the Alpheus coast have been credited with the founding of the city in the 'Etruscan lands'. The Virgilian commentator Servius wrote that the Teuti, or Pelops, the king of the Pisaeans, founded the town thirteen centuries before the start of the common era.
The maritime role of Pisa should have been already prominent if the ancient authorities ascribed to it the invention of the naval ram. Pisa took advantage of being the only port along the western coast from Genoa (then a small village) to Ostia. Pisa served as a base for Roman naval expeditions against Ligurians, Gauls and Carthaginians. In 180 BC, it became a Roman colony under Roman law, as Portus Pisanus. In 89 BC, Portus Pisanus became a municipium. Emperor Augustus fortified the colony into an important port and changed the name in Colonia Iulia obsequens.
It is supposed that Pisa was founded on the shore. However, due to the alluvial sediments from the Arno and the Serchio, whose mouth lies about 11 kilometres (7 mi) north of the Arno's, the shore moved west. Strabo states that the city was 4.0 kilometres (2.5 mi) away from the coast. Currently, it is located 9.7 kilometres (6 mi) from the coast. However it was a maritime city, with ships sailing up the Arno. In the 90s AD, a baths complex was built in the city.