An Etymological Dictionary of the German Language/Annotated/Spiegel
Spiegel, masculine, ‘mirror, looking-glass, reflector,’ from the equivalent Middle High German spiegel, Old High German spiagal, masculine (compare Dutch spiegel). The Old High German term is derived, with a change of gender, from Middle Latin spêgulum (equivalent to Latin spĕculum), to which Italian speglio (also specchio), ‘mirror,’ points. The word must have been borrowed, on account of the change of vowels, prior to the Old High German period. Old Teutonic has a peculiar word for ‘mirror’; compare Old High German scûchar, literally ‘shadow container,’ from Old High German scûwo, Anglo-Saxon sčûa, ‘shadow,’ in Gothic skuggwa, ‘mirror.’