An Etymological Dictionary of the German Language/Annotated/Fenster
Fenster, neuter, ‘window,’ from the equivalent Middle High German vęnster, Old High German vęnstar, neuter; compare Dutch venster, neuter. Based, with a curious change of gender, on Latin fenestra, from which, however, the fęnstar of the Middle European Teutons could only be produced by shifting the accent back according to the Teutonic custom (compare Abt) and by syncopating the second e. This indicates that the word was borrowed very early, in the beginning of the Old High German period. Yet the idea was well known to the older periods, as is testified by the terms naturally applied to the existing object — Gothic augadaurô, ‘eye-gate,’ Anglo-Saxon êgþŷrel, ‘eye-hole,’ Old Icelandic vindauga (whence Middle English windôge, English window). By the introduction of the Southern term (compare also Old Irish senister, Welsh ffenester) the idea was probably reconstructed. This word was borrowed at the same period as other words — Ziegel, Mauer — relating to the building of houses.