Their memory also survives in the modern regional names of Bohemia (Germanic form found in a Roman source Boio-haemum = home of the Boii), and 'Bayern', Bavaria, which is derived from the Germanic Baiovarii tribe (Germ. *baio-warioz: the first component is most plausibly explained as a Germanic version of Boii; the second part is a common formational morpheme of Germanic tribal names, meaning 'dwellers', as in Anglo-Saxon -ware); this combination "Boii-dwellers" may have meant "those who dwell where the Boii formerly dwelt".
In the second half of the 3rd century BC, the Boii allied with the other Cisalpine Gauls and the Etruscans against Rome. They also fought alongside Hannibal, killing the Roman general L. Postumius Albinus, whose skull was then turned into a sacrificial bowl (Liv. XXIII, 24). A short time thereafter, they were defeated at Telamon in 224 BC and eventually in 193 BC near Mutina (modern Modena). After the loss of their capital, a large portion of the Boii left Italy. Contrary to the interpretation of the classical writers, the Pannonian Boii attested in later sources are not simply the remnants of those who had fled from Italy, but rather another division of the tribe, which had settled there much earlier. The burial rites of the Italian Boii show many similarities with contemporary Bohemia, such as inhumation, which was uncommon with the other Cisalpine Gauls, or the absence of the typically western Celtic torcs. This makes it much more likely that the Cisalpine Boii had actually originated from Bohemia rather than the other way round. Having migrated to Italy from north of the Alps, some of the defeated Celts simply moved back to their kinsfolk.
The Pannonian Boii are mentioned again in the late 2nd century BC when they repelled the Cimbri and Teutones (Strabo VII, 2, 2). Later on, they attacked the city of Noreia (in modern Austria) shortly before a group of Boii (32,000 according to Julius Caesar - the number is probably an exaggeration) joined the Helvetii in their attempt to settle in western Gaul. After the Helvetian defeat at Bibracte, the influential Aedui tribe allowed the Boii survivors to settle on their territory, where they occupied the oppidum of Gorgobina. Although attacked by Vercingetorix during one phase of the war, they supported him with two thousand troops at the battle of Alesia (Caes. Bell. Gall., VII, 75).
Again, other parts of the Boii had remained closer to their traditional home, and settled in the Hungarian lowlands by the Danube and the Mur, with a centre at Bratislava. Around 40 BC they clashed with the rising power of the Dacians under their king Burebista and were defeated. When the Romans finally conquered Pannonia in 8 AD, the Boii seem not to have opposed them. Their former territory was now called deserta Boiorum (deserta meaning 'empty or sparsely populated lands'). However, the Boii had not been exterminated: There was a civitas Boiorum et Azaliorum (the Azalii being a neighbouring tribe) which was under the jurisdiction of a prefect of the Danube shore (praefectus ripae Danuvii). This civitas, a common Roman administrative term designating both a city and the tribal district around it, was later adjoined to the city of Carnuntum.
In the 1st century BC, the Boii living in an oppidum of Bratislava (Slovakia) minted Biatecs, high-quality coins with inscriptions (probably the names of kings) in Latin letters. This is the only "written source" provided by the Boii themselves.