Why did the Porsche 901 have its name changed to the now-iconic 911 name?

The Porsche 911 was first unveiled to the public on 12 September 1963 when it was launched at the Frankfurt International Motor Show. (...) The second production model to be made by the company after the Porsche 356, interestingly the 911 was originally called the 901. However, by the time the model went on sale it had become the 911 after a claim about naming rights from French car manufacturer, Peugeot.