Appian(us) (c.AD 95 – c. 165) was born in Alexandria but went to Rome in c.120 to practice law. We are not entirely sure about what sources he used for his histories.
The following is an adaptation of Appian. The Foreign Wars, trans. Horace White. New York: MacMillan Company, 1899.
§ 1. [218 BCE] […] What Hannibal himself and what the other Carthaginian and Roman generals after him did in Spain, I have related in the Spanish history. Having collected a large army of Celtiberians, Africans, and other nationalities, and put the command of Spain in the hands of his brother Hasdrubal, he crossed over the Pyrenees mountains into the country of the Celts, which is now called Gaul, with 90,000 foot, 12,000 horse, and 37 elephants. He passed through the country of the Gauls, conciliating some with money and some by persuasion, and overcoming others by force. When he came to the Alps and found no road through or over them (for they were exceedingly precipitous), he nevertheless marched boldly forward, but suffered great losses.
§ 2. […] After a brief pause he attacked Taurasia, a Gallic town, took it by storm, and put the prisoners to death, in order to strike terror into the rest of the Gauls. Then he advanced to the river Eridanus, now called the Padus [Po], where the Romans were at war with the Gallic nation called the Boii, and pitched his camp. The Roman consul, Publius Cornelius Scipio, was at that time contending with the Carthaginians in Spain. When he learned of Hannibal’s incursion into Italy, he left his brother, Gnæus Cornelius Scipio, in charge of affairs in Spain and sailed for Etruria. Marching thence with such allies as he could collect, he came before Hannibal to the Po. He sent Manlius and Atilius, who were conducting the war against the Boii, back to Rome, as they had no right to command when a consul was on the ground, and taking their forces drew them up for battle with Hannibal. After a skirmish and a cavalry engagement, the Romans were surrounded by the Africans and fled to their camp. The next night they took refuge in Placentia, a place strongly fortified, crossing the Po and then breaking down the bridge. Nevertheless Hannibal made a new bridge and crossed the river.
These exploits, one after another, following his passage of the Alps, exalted Hannibal’s fame among the Cisalpine Gauls as an invincible commander and one most highly favored by fortune. In order to increase the admiration of those barbarians, who were easily deceived, he frequently changed his clothes and his hair, using carefully prepared devices each time. When the Gauls saw him moving among their people now an old man, then a young man, and again a middle-aged man, and continually changing from one to the other, they were astonished and thought that he partook of the divine nature.
[…] The Apennines extend from the centre of the Alpine range to the sea. The country on the right-hand side of the Apennines is Italy proper. The other side, extending to the Adriatic, is now called Italy also, just as Etruria is now called Italy, but is inhabited by people of Greek descent, along the Adriatic shore, the remainder being occupied by Gauls, the same people who at an early period attacked and burned Rome. When Camillus drove them out and pursued them to the Apennines, it is my opinion that they crossed over these mountains and made a settlement near the Adriatic instead of their former abode. Hence this part of the country is still called Gallic Italy.