Pannonia (, ) was a province of the Roman Empire bounded on the north and east by the Danube, coterminous westward with Noricum and upper Italy, and southward with Dalmatia and upper Moesia. Pannonia was located in the territory that is now western Hungary, western Slovakia, eastern Austria, northern Croatia, north-western Serbia, northern Slovenia, and northern Bosnia and Herzegovina. Name Julius Pokorny believed the name Pannonia is derived from Illyrian, from the Proto-Indo-European root *pen-, "swamp, water, wet" (cf. English fen, "marsh"; Hindi pani, "water"). Pliny the Elder, in Natural History, places the eastern regions of the Hercynium jugum, the "Hercynian mountain chain", in Pannonia and Dacia (now Romania). He also gives us some dramaticised description of its composition, in which the proximity of the forest trees causes competitive struggle among them (inter se rixantes). He mentions its gigantic oaks. But even he—if the passage in question is not an interpolated marginal gloss—is subject to the legends of the gloomy forest. He mentions unusual birds, which have feathers that "shine like fires at night". Medieval bestiaries named these birds the Ercinee. The impenetrable nature of the Hercynia Silva hindered the last concerted Roman foray into the forest, by Drusus, during 12–9 BC: Florus asserts that Drusus invisum atque inaccessum in id tempus Hercynium saltum (Hercynia saltus, the "Hercynian ravine-land") patefecit. History Prior to Roman conquest The first inhabitants of this area known to history were the Pannonii (Pannonians), a group of Indo-European tribes akin to Illyrians. From the 4th century BC, it was invaded by various Celtic tribes. Trade flourished between Latins and Celts for one and a half century before the sudden Roman invasion. The country was not, however, definitively subdued by the Romans until 9 BC, when it was incorporated into Illyricum, the frontier of which was thus extended as far as the Danube. Under Roman rule The expansion of Dacians into Pannonia pressured Rome to prevent them from fully conquering it. Cotiso was defeated by Augustus and with his death in 9 BC, Pannonia fully came under Roman control. In AD 6, the Pannonians, with the Dalmatians and other Illyrian tribes, engaged in the so-called Great Illyrian Revolt, and were overcome by Tiberius and Germanicus, after a hard-fought campaign, which lasted for three years. After the rebellion was crushed in AD 9, the province of Illyricum was dissolved, and its lands were divided between the new provinces