bheh₂ǵ-es-
“beech tree, its nut”beech, book, buckwheat
Root yielding English beech, book (from writing on beech bark), buckwheat.
Discussion
The Proto-Indo-European form *bheh₂ǵ-es- reconstructs as an s-stem neuter noun designating the beech tree and, by extension, its edible nut. This particular etymon has occupied a position of outsized importance in Indo-European studies since the nineteenth century, for it stands at the center of the so-called "beech argument" (Buchenargument), the biogeographical reasoning that attempts to locate the Proto-Indo-European homeland by mapping the natural range of Fagus sylvatica against the distribution of cognate tree names. Pokorny (IEW 107) assembles the cognate set under *bhāg̑o-s, and the argument, though now regarded with considerable skepticism, held that since the European beech does not grow east of a line running from Königsberg to the Crimea, the PIE speakers must have inhabited a territory west of that boundary.
The reflex in Latin, fāgus "beech," preserves the root with regular development of the aspirated labiovelar. Germanic *bōkō- produced Old English bōc, Modern English beech, and German Buche. The most consequential semantic extension, however, occurred within Germanic itself: because early runic inscriptions were carved on tablets of beechwood, the word for the tree transferred to the writing medium, yielding Old English bōc "book," German Buch, and the entire modern family of bookish vocabulary — a semantic journey from forest to library that is one of the most culturally revealing in the Germanic lexicon.
Greek φηγός (phēgós), however, designates not the beech but the Valonia oak, a semantic shift that Beekes considers fatal to the strict form of the beech argument, since it demonstrates that cognate forms could be reassigned to locally prominent tree species as populations migrated into new ecological zones. The lesson of *bheh₂ǵ-es- is thus double: it reveals both the possibilities and the perils of using botanical vocabulary as a compass for prehistoric geography, reminding us that words migrate with peoples but attach themselves to whatever landscape those peoples find.