An Etymological Dictionary of the German Language/Annotated/Buche
Buche, feminine, ‘beech, beech-tree,’ from the equivalent Middle High German buoche, Old High German buohha; Anglo-Saxon bôc-treów, with the collateral form bêce (from boeciae), English beech. The form bôc has been preserved in English buckmast, buckwheat; compare Old Icelandic bók, Gothic *bôka, ‘beech.’ The name of the tree is derived from pre-Teutonic; according to Latin fâgus, ‘beech,’ and Greek φᾶγός, φηγός, its European form would be bhâgos. The Greek word signifies ‘edible oak.’ This difference between the Greek word on the one hand and the Teutonic-Latin on the other has been explained “by the change of vegetation, the succession of an oak and a beech period”; “the Teutons and the Italians witnessed the transition of the oak period to the beech period, and while the Greeks retained φηγός in its originally signification, the former transferred the name as a general term to the new forests which grew in their native wastes.” Compare Eiche. Buche is properly ‘the tree with edible fruit’ (compare Greek φαγεῖν, ‘to eat,’ and φηγός), and hence perhaps the difference of meaning in Greek may be explained from this general signification, so that the above hypothesis was not necessary.