The Samnites were an Oscan-speaking people, and they were probably an offshoot of the Sabines. The Samnites formed a confederation of the tribes Hirpini, Caudini, Caraceni, and Pentri. They were allied with Rome against the Gauls in 354 BC, but later became enemies of the Romans and were soon involved in a series of three wars (343–341, 327–304, and 298–290) against the Romans. Despite a spectacular victory over the Romans at the Battle of the Caudine Forks (321), the Samnites were eventually subjugated. Although severely weakened, the Samnites later helped Pyrrhus and Hannibal in their wars against Rome. They also fought from 90 BC in the Social War and later in the civil war as allies of Gnaeus Papirius Carbo against Lucius Cornelius Sulla, who defeated them and their leader Pontius Telesinus the Battle of the Colline Gate (82 BC). By 82 BC, the Roman dictator Lucius Cornelius Sulla conducted an ethnic cleansing campaign against the Sabines, after which they disappeared from history.
Etymologically the name Samnium is generally recognized to be a form of the name of the Sabines, who were Umbrians. From Safinim, Sabinus, Sabellus and Samnis an Indo-European root can be extracted, *sabh-, which becomes Sab- in Latino-Faliscan and Saf- in Osco-Umbrian: Sabini and *Safineis. The eponymous god of the Sabines, Sabus, seems to support this view. The Greek terms, Saunitai and Saunitis, remain outside the group. Nothing is known of their origin.
At some point in prehistory, a population speaking a common language extended over both Samnium and Umbria. Salmon conjectures that it was common Italic and puts forward a date of 600 BC, after which the common language began to dialectize. This date does not necessarily correspond to any historical or archaeological evidence; developing a synthetic view of the ethnology of proto-historic Italy is an incomplete and ongoing task.
Linguist Julius Pokorny carries the etymology somewhat further back. Conjecturing that the -a- was altered from an -o- during some prehistoric residence in Illyria he derives the names from an o-grade extension *swo-bho- of an extended e-grade *swe-bho- of the possessive adjective, *s(e)we-, of the reflexive pronoun, *se-, "oneself" (the source of English self). The result is a set of Indo-European tribal names (if not the endonym of the Indo-Europeans): Germanic Suebi and Semnones, Suiones; Celtic Senones; Slavic Serbs and Sorbs; Italic Sabelli, Sabini, etc., as well as a large number of kinship terms. The general concept is "our own kith and kin," Pokorny's "von eigener Art," "Gesamtheit der eigenen Leute," "Liebe," "Sippegenossen," "Sippenangehörigen," and the like.
The earliest written record of the people is a treaty with the Romans from 354 BC, which set their border at the Liris River. Shortly thereafter the Samnite Wars broke out; they won an important battle against the Roman army in 321 BC, and their imperium reached its peak in 316 BC after further gains from the Romans. By 290 BC, the Romans were able to break the Samnites' power after some hard fought battles. The Samnites were one of the Italian peoples that allied with King Pyrrhus of Epirus during the Pyrrhic War. After Pyrrhus left for Sicily, the Romans invaded Samnium and were crushed at the Battle of the Cranita hills, but after the defeat of Pyrrhus the Samnites could not resist on their own and submitted to Rome. They joined and aided Hannibal during the Second Punic War. The Samnites were the last tribal group holding out against Rome in the Social War (91–88 BC). By 82 BC, the Roman dictator Lucius Cornelius Sulla conducted an ethnic cleansing campaign against this most stubborn and persistent of Rome's adversaries and forced the remnant to disperse. So great was the destruction brought upon them that it was recorded that "the towns of Samnium have become villages, and most have vanished altogether.".