I found that out in 1966, the last time I visited Belgium. As we traveled southbound on a highway out of Ghent, we followed road signs to a place called Bergen. However, we never got there. When we completed the distance to Bergen as displayed in the signs, we found ourselves in a city called Mons, for we had crossed from the Flemish-speaking to the French-speaking part of Belgium.
Well...some of it is French but most of it is not. It may sound French, but it isn’t. Those I know up around Brussels WI can not understand French.
Like the name Gauthier. It’s pronounced Goe-chee in most French quarters. The name Potier is prounced Put-chee everywhere. In that local Waloon dialect, they are pronounced entirely different.
I wonder if some of the dialects are based on the old Norman dialect.