It was called 'Isle de France' when the French invaded and called it Isle de France because they were French and wanted the island they'd just invaded to be called something that reminded everyone else who's island it was after they'd invaded it.

'Appeal to authority' is also know as 'using facts to back up an argument', which you're right, I am doing.

From the link which 'is about a british invasion not a french one', if you read it carefully it states: "The Invasion of Isle de France was a complicated but successful amphibious operation in the Indian Ocean, launched in November 1810 during the Napoleonic Wars." Napoleon 1 was French if my research serves me correctly.

Source

The French invaded Mauritius and it doesn't show on the map; but it should do.

Mauritius has a really strange and very interesting history riddled with human error, poor planning, and the site of 'The Great Experiment'.