"Illyrius had six sons, Encheleus, Autarieus, Dardanus, Maedus, Taulas, and Perrhaebus, also daughters,
Partho, Daortho, Dassaro.
And others, from whom sprang the Taulantii, the Perrhaebi, the Enchelees, the Autarienses, the Dardani, the Partheni, the Dassaretii, and the Darsii.
Autarieus had a son Pannonius, or Paeon, and the latter had sons, Scordiscus and Triballus, from whom nations bearing similar names were derived".

Appian, The Foreign Wars:

A decisive expedition takes place in IVth century BC for control of the Amber road. Under the Greeks, amber went due east, across the Austrian Gap at Vienna, along the Danube River to the Black Sea. Then by land or sea through the Bosphorous and Dardanelles into the Aegean. In 225 BCE, the Romans inflicted their first major defeat upon the Celts, who at this time occupied the entire Po valley. Whatever amber managed to get into Italy came by way of the sea, or as trade through the Celts. During the first millennium BCE, Rome was beginning to push the Celts back into upper Germany. However, the amber source, the Baltic Sea, still remained out of Rome's direct control. By now routes were open to the Danube valley, and an overland amber route established. This went from the head of the Adriatic Sea around the east flank of the Alps and through Austria and Poland to the Baltic.

Coming down from the Black Forest and following along the Danube's banks. They are stopped by an Illyrian people, the Antariates. These wars last fifty years and Celts, having subjected them, towards 310BC, settle on their place. The Macedonian empire stands in their way, so the Celts spread northwards in the direction of Transylvania. As demand for amber grew, Rome became more interested in cutting out the middlemen and dealing direct with the source, where-ever that was. Emperor Nero sent a small exploration party up the amber trail with orders to seek out the source. When the soldiers returned, they carried with them a huge load of amber, and the news that the source was so far away that Rome could never protect those sent to take it.

In the third century B.C., Rome conquered the west Adriatic coast and began exerting influence on the opposite shore. Greek allegations that the Illyrians were disrupting commerce and plundering coastal towns helped precipitate a Roman punitive strike in 229 B.C., and in subsequent campaigns Rome forced Illyrian rulers to pay tribute. Roman armies often crossed Illyria during the Roman-Macedonian wars, and in 168 B.C. Rome conquered the Illyrians and destroyed the Macedonia of Philip and Alexander. For many years the Dinaric Alps sheltered resistance forces, but Roman dominance increased. In 35 B.C., the emperor Octavian conquered the coastal region and seized inland Celtic and Illyrian strongholds; in A.D. 9, Tiberius consolidated Roman control of the western Balkan peninsula; and by A.D. 14, Rome had subjugated the Celts in what is now Serbia.
Over half the route was through the lands of their ancient enemy, the Celts. While at the moment they were peaceful, they could not be trusted, especially if Rome was to take away such a lucrative source of income. If Rome could not control the source, they could at least make the distance as short as possible and cut the price of amber down a bit. With this in mind, Emperor Claudius set out to pave a road across the Alps.