Besides the German origin I've also read about an ancient Greek origin for this name. As name etymology is quite complex and sometimes based on guess, this one origin might be valid, I think. From "Alea" (a Greek goddess previous to the Greek pantheon we all know, that later joined Athina as both goddesses were very similar, becoming Aleas Athina) and "eydos" (meaning "outward appearance, external fashion, form and figure, look".) Nice meaning, isn't it? :)
I wonder whether this name is common or old-fashioned. And exactly in which countries or regions it is nowadays used. I know it's used in north-east Spain, in the region called Catalonia. Through Catalonia's Statistic Institute I've found out there are about 5,000 Catalan woman with this name out of 7 million inhabitants. Any similar information regarding this on other countries?