Bilingualism in North-East France with specific reference to Rhenish Franconian spoken by Moselle Cross-border (or frontier) workers - Stephanie Hughes University of Antwerp (PDF)
To the north, it is bounded by the Sankt Goar line (“das/dat line”) which separates it from MoselleFranconian; to the south, it is bounded by the Main line which is also referred to as the Speyer line which separates it from the Upper German dialects.
Franconian refers to the Franks that settled in Germany, France, and the Low Countries between 200 and 400 A.D. Various languages and dialects, which are supposed to have developed from the Old Frankish language of the Franks, have been given the name of Franconian.
Rather, West Franconian (also called MoselleFranconian or Frankish) refers to the High German languages and/or dialects of Luxembourg, the Saarland, Lorriane, the Eifel area of Germany, and portions of Belgium.
Low Franconian refers to the varieties of the language spoken in the Netherlands (Dutch), and southern Africa (Afrikaans).