An Etymological Dictionary of the German Language/Annotated/Forst
Forst masculine, ‘forest, wood,’ from Middle High German vorst, Old High German forst, masculine, ‘wood’; also the Middle High German variants vŏrëst, fŏrest, fŏrest, fŏreist (but probably not fôrest), neuter, ‘wood, forest’; these forms are certainly of Romance origin, — Middle Latin and Romance foresta, whence French forêt. It is questionable whether the Old High German forst, vorst, masculine, are also derived from Romance. Opinions are divided on this point; some etymologists connect the Romance word with Latin foris, ‘outside’; others more probably refer Old High German forst to Old High German foraha, ‘fir’; hence forst would be literally ‘fir wood.’ Old High German forst might also be connected with Gothic faírguni, ‘mountain.’ Gothic *faúrst for faúrhst, ‘mountain forest,’ would have to be construed like the assumed Gothic *faúrskôn for *faúrhskôn, mentioned under forschen.