Just a wink to the ridiculous conflict that goes on between French-speaking-Belgians and the Dutch-speaking-Belgians, now for years.
If you called them that in Belgium I bet you would cause a riot. ;-)
Slightly thicker (square) fries are just called fries (patat): http://i.imgur.com/tui5FDe.jpg. These are served most often.
The big rectangular fries are referred to as Flemish fries (vlaamse frieten): http://i.imgur.com/QDwv9IA.jpg.
Just a wink to the ridiculous conflict that goes on between French-speaking-Belgians and the Dutch-speaking-Belgians, now for years.