An Etymological Dictionary of the German Language/Annotated/Föhre
Föhre, feminine, ‘fir,’ from Middle High German vorhe, Old High German forha, feminine, ‘pine-tree’; corresponding to Anglo-Saxon furh, feminine, English fir (Middle English firre, formed from Danish fyr), Old Icelandic fura, feminine, ‘fir’; Gothic *faúrhus, feminine, is wanting. If the initial f is to be regarded as in vier related to Latin quattuor, Föhre may be connected with Latin quercus, ‘oak’; for the change of meaning Eiche and Tanne might be compared. In earlier Modern High German Ferch, ‘oak,’ is also recorded once, and is akin to Old High German vereh-eih, Lombardic fereha, ‘æsculus.’ Thus the connection between Föhre and quercus (pre-Teutonic qṛku-) is certain. In any case, Feuer is not a cognate. Fichte, Birke, Buche, Föhre are the few names of trees whose existence can be traced beyond Teutonic. Compare also Kiefer.