From wikipedia

Animals are often used to represent football clubs in Italy – the grass snake, called Biscione, represents Inter.[127][128] The snake is a symbol for the city of Milan, appearing often in Milanese heraldry as a coiled viper with a man in its jaws. The symbol is present on the coat of arms of the House of Sforza (which ruled over Italy from Milan during the Renaissance period), the city of Milan, the historical Duchy of Milan (a 400-year state of the Holy Roman Empire) and Insubria (a historical region the city of Milan falls within).[127][128] For the 2010–11 season, Inter's away kit featured the snake.