Short answers, pulled from the story.
The name Arverni appears in texts from the mid-1st century BC written by Julius Caesar. Scholars debate the meaning of the original Gaulish word *Aruernoi with Pierre-Yves Lambert suggesting it means those who are above.
Ancient maps place the Arverni east of the Lemovices and Petrocorii tribes living south of the Bituriges Cubi and Aedui peoples. Their territory covered parts of Puy-de-Dôme and Cantal departments including small areas of Haute-Loire and Allier.
King Luernius led the Arverni during the mid-2nd century BC and scattered gold and silver coins to his followers while riding a chariot. Under Luernius the tribe held military power from the Rhine to the Atlantic coast.
The Battle of Isère River took place in 121 BC between Romans and Arverni forces commanded by Quintus Fabius Maximus and Gnaeus Ahenobarbus against King Bituitus. Defeat at this battle ended Arvernian supremacy over neighboring peoples.
Vercingetorix declared himself king in 52 BC after expelling his uncle Gobanitio from Gergovia and rallied supporters to fight Julius Caesar following the execution of his father Celtillus. He forged alliances with at least fifteen Gallic tribes to resist Roman rule.