Others believe that the name is related to the god of the nature, goats and shepherds Pan and/or pan, the Proto-Slavic/Proto-Indo-European word for lord/master, which could mean Pan's Land or Land of the Master(s), which is more probable due the fact the Ionian fleet supplied Pannonia via Black Sea and Danube, and Panionium festivities were also well known in the region to its Celtic, Adriatic Veneti and Scythian inhabitants. The Ionian Danube fleet reached as far as Boio-Aria (Bavaria), populated until the late 8th century CE by Celts and Slavs under Aryan rulers (druids, župans).
Pliny the Elder, in Natural History, places the eastern regions of the Hercynium jugum, the "Hercynian mountain chain", in Pannonia (present-day Hungary) and Dacia (present-day Romania). He also gives us some dramaticised description of its composition, in which the close 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 Hercynian Silva hindered the last concerted Roman foray into the forest, by Drusus, during 12..9 BCE: Florus asserts that Drusus invisum atque inaccessum in id tempus Hercynium saltum (Hercynia saltus, the "Hercynian ravine-land") patefecit.
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. Little is heard of Pannonia until 35 BC, when its inhabitants, allies of the Dalmatians, were attacked by Augustus, who conquered and occupied Siscia (Sisak). 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.
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 of Pannonia in the north and Dalmatia in the south. The date of the division is unknown, most certainly after AD 20 but before AD 50. The proximity of dangerous barbarian tribes (Quadi, Marcomanni) necessitated the presence of a large number of troops (seven legions in later times), and numerous fortresses were built on the bank of the Danube.