The Italian word Lazio descends from the Latin word Latium. The name of the region also survives in the tribal designation of the ancient population of Latins, Latini in the Latin language spoken by them and passed on to the city-state of Ancient Rome. Although the demography of ancient Rome was multi-ethnic, including, for example, Etruscans and other Italics besides the Latini, the latter were the dominant constituent. In Roman mythology, the tribe of the Latini took their name from King Latinus. Apart from the mythical derivation of Lazio given by the ancients as the place where Saturn, ruler of the golden age in Latium, hid (latuisset) from Jupiter there, a major modern etymology is that Lazio comes from the Latin word "latus", meaning "wide", expressing the idea of "flat land" meaning the Roman Campagna. Much of Lazio is in fact flat or rolling. The lands originally inhabited by the Latini were extended into the territories of the Samnites, the Marsi, the Hernici, the Aequi, the Aurunci and the Volsci, all surrounding Italic tribes. This larger territory was still called Latium, but it was divided into Latium adiectum or Latium Novum, the added lands or New Latium, and Latium Vetus, or Old Latium, the older, smaller region. The northern border of Lazio was the Tiber river, which divided it from Etruria.