An Etymological Dictionary of the German Language/Annotated/Grenze
Grenze, feminine, ‘boundary, frontier, limit,’ from the equivalent late Middle High German gręniz, gręnize, feminine (appeared in the 13th century in the district belonging to the Teutonic Order), which is again derived from Polish and Russian granica, Bohemian hranice. The native word for Grenze is Warf.