Toulouse has been inhabited since the 8th century B.C. The original settlers lived in the hills overlooking the Garonne, a few kilometres south of today's city center. The site was also conveniently located between the Pyrénées, the Mediterranean and the Atlantic, which helped make it a major trading center.
Toulouse's first name was Tolosa. Julius Caesar also called it Tolosates. Overall, though, the name has not changed much over the centuries.
According to Wikipedia, the city "was one of the wealthiest and most important cities in Gaul during the pre-Roman era. Gold and silver mines were nearby, and offerings to its shrines and temples accumulated wealth in the city."