They first appear in history in connection with the Gallic invasion of north Italy, 390 BC, when they made the Etruscan city of Felsina their new capital, Bononia (Bologna). After a series of wars they were decisively beaten by the Romans in a Battle of Mutina (193 BC) and their territory became part of the Roman province of Cisalpine Gaul. According to Strabo, writing two centuries after the events, rather than being destroyed by the Romans like their Celtic neighbours,
he Boii were merely driven out of the regions they occupied; and after migrating to the regions round about the Ister, lived with the Taurisci, and carried on war against the Daci until they perished, tribe and all — and thus they left their country, which was a part of Illyria, to their neighbours as a pasture-ground for sheep.
Around 60 BC, a group of Boii joined the Helvetii's ill-fated attempt to conquer land in western Gaul and were defeated by Julius Caesar, along with their allies, in the battle of Bibracte. Caesar settled the remnants of that group in Gorgobina, from where they sent two thousand to Vercingetorix's aid at the battle of Alesia six years later. The eastern Boii on the Danube were incorporated into the Roman Empire in 8 AD.
From all the different names of the same Celtic people in literature and inscriptions it is possible to abstract a Continental Celtic segment, boio-. There are two major derivations of this segment, both presupposing that it belongs to the family of Indo-European languages: from 'cow' and from 'warrior.' The Boii would thus be either "the herding people" or "the warrior people."
The "cow" derivation depends most immediately on the Old Irish legal term for "outsider:" ambue, from Proto-Celtic *ambouios (<*an-bouios), "not a cattle owner." In a reference to the first known historical Boii, Polybius relates that their wealth consisted of cattle and gold, that they depended on agriculture and war, and that a man's status depended on the number of associates and assistants he had. The latter were presumably the *ambouii, as opposed to the man of status, who was *bouios, a cattle owner, and the *bouii were originally a class, "the cattle owners."