The Hercynian Forest was an ancient and dense forest that stretched across Western Central Europe, from Northeastern France to the Carpathian Mountains, including most of Southern Germany, however its boundaries are a matter of debate. It formed the northern boundary of that part of Europe known to writers of Antiquity. The ancient sources are equivocal about how far east it extended. Many agree that the Black Forest, which extended east from the Rhine valley, formed the western side of the Hercynian, except, for example, Lucius of Tongeren. According to him, it included many massifs west of the Rhine. Across the Rhine to the west extended the Silva Carbonaria, the forest of the Ardennes and the forest of the Vosges. All these old-growth forests of antiquity represented the original post-glacial temperate broadleaf forest ecosystem of Europe. Relict tracts of this once-continuous forest exist with many local names: the Black Forest, the Ardennes, the Bavarian Forest, the Vosges, the Eifel, the Jura Mountains, the Swabian Jura, the Franconian Jura, the Polish Jura, the Palatinate Forest, the Teutoburg Forest, the Argonne Forest, the Morvan, the Langres plateau, the Odenwald, the Spessart, the Rhön, the Thuringian Forest, the Harz, the Rauhe Alb, the Steigerwald, the Fichtel Mountains, the Ore Mountains, the Giant Mountains, the Bohemian Forest and the Sudetes. In present-day Czech Republic and southern Poland, it joined the forested Carpathians. The Mittelgebirge seem to correspond more or less to a stretch of the Hercynian mountains. Many present-day smaller forests were also included like the Bienwald and the Haguenau Forest. The Hercynian Forest maybe extended northwest to the Veluwe and east to the Białowieża Forest. Etymology Hercynian has a Proto-Celtic derivation, from ɸerkuniā, later erkunia. Julius Pokorny lists Hercynian as being derived from * "oak" (compare quercus). He further identifies the name as Celtic. Proto-Celtic regularly loses initial preceding a vowel, hence the earliest attestations in Greek as Ἀρκόνια (Aristotle, the e~a interchange common in Celtic names), later Ὀρκύνιος (Ptolemy, with the o unexplained) and Ἑρκύνιος δρυμός (Strabo). The latter form first appears in Latin as Hercynia in Julius Caesar, inheriting the aspiration and the letter y from a Greek source. The Germanic forms appear with an f for *p by Grimm's Law, indicating an early borrowing from Celtic before it lost the initial consonant: Gothic faírguni = "mountain, mountain range", Old English firgen = "mountain, mountain-woodland". The assimilated would be regular in Italo-Celtic,