Titus Livius (Livy), The History of Rome, Book 5
Benjamin Oliver Foster, Ph.D., Ed.

33. After the expulsion of that citizen whose presence, if anything in this life is certain, would have made the capture of Rome impossible, disaster approached the ill-fated City with the arrival of [p. 115]envoys from the men of Clusium seeking help¹ against the Gauls. [2] The story runs that this race, allured by the delicious fruits and especially the wine —then a novel luxury —had crossed the Alps and possessed themselves of lands that had before been tilled by the Etruscans; [3] and that wine had been imported into Gaul expressly to entice them, by Arruns of Clusium, in his anger at the seduction of his wife by Lucumo. This youth, whose guardian he had been, was so powerful that he could not have chastised him without calling in a foreign force. [4] He it was who is said to have guided the Gauls across the Alps, and to have suggested the attack on Clusium. Now I would not deny that Arruns or some other citizen brought the Gauls to Clusium, but that those who besieged Clusium were not the first who had passed the Alps is generally agreed. [5] Indeed it was two hundred years before the attack on Clusium and the capture of Rome, that the Gauls first crossed over into Italy; neither were the Clusini the first of the Etruscans with whom they fought; [6] but long before that the Gallic armies had often given battle to those who dwelt between the Apennines and the Alps.

[7] The Tuscan sway, down to the rise of the Roman domination, stretched over a wide expanse of land and sea. How great their power was on the upper and the lower seas, by which Italy is surrounded like an island, is apparent from the names, since the Italian races have called one of them Tuscan, the [8??] general designation of the race, and the other Hadriatic, from Hatria, an Etruscan colony; and the Greeks know the same seas as Tyrrhenian and Adriatic. [9] In the lands which slope on either side [p. 117]towards one of these seas, they had twice twelve² cities; first the twelve on this side the Apennines, towards the lower sea; [10] to which afterwards they added the same number beyond the Apennines, sending over as many colonies as there were original cities, and taking possession of all the transpadane region (except the angle belonging to the Veneti who dwell about the gulf) as far as the Alps. [11] The Alpine tribes have also, no doubt, the same origin, especially the Raetians; who have been rendered so savage by the very nature of the country as to retain nothing of their ancient character save the sound of their speech, and even that is corrupted.