I fixed the map
Background at ALOTT5MA
Map copied from here.
Earliest "Walloon" reference in the New York Times is October 11, 1853. From NY Times, January 3, 1883: FRANCE AND HER ENEMIES; TERRITORY THEY SEEK AND THE STATE OF HER ARMY:
“Read Boedecker's last edition of the "Guide to Belgium," and one can convince himself that Lille and Reissel are on the Belgian map, and that a line of separation of Flemish and Walloon populations from French populations is drawn from Leige to Calais. Boedecker gives no explanation of this innovation, nor have the Belgians yet announced when they propose to annex France; yet the work of the propagandism is actively pursued, and in the rural districts around Lille Belgian book-peddlers distribute gratuitously thousands of maps on which French Flanders is represented as incorporated with Belgium.
May 30, 1915, REMAKING THE MAP OF EUROPE; Jean Finot's Views on How Parts of Germany and Austria-Hungary Should Be Redistributed in Case the Allies Win.