Judendorf was first mentioned in Christian records in the 12 th century. Gerhard Salzer - Eibenstein writes (in Geschichte der Juden in Sudost-Osterreich, Graz 1988) that in old property records from the 12 and 13th century there are descriptions of property defined as a "village near the Jews" (derived from Latin, the official language at the time, "villa ad iudeos"), in short "Judendorf" -- even though there are no records or memory that Jews ever lived in such places.
There are many Judendorfs in Austria. We went to the Judendorf near Villach, but there is also a Judendorf bei Maria Saal, a Judendorf bei Friesach, Tamsweg, Leoben, Steyr, and elsewhere. Salzer-Eibenstein believes that the Jewish presence in these areas in the early middle ages were nothing more than small Jewish households, consisting of a poor homestead with a barn where a traveling Jewish merchant could stay for a night, rest his animals, and have a kosher meal. These homesteads were located, near, but not within the village.
However, Salzer Eibenstein's historical research (especially regarding the presence of a Jewish ghetto in Graz) has been criticized by recent historians so we don't know how reliable the above hypothesis now is.
There is quite a bit of evidence, in any case, that a sizable Jewish community did live in JudenBURG - which even today shows a man wearing a "judenhut" from the middle ages on the city's coat of arms!
Jewish settlements began to grow in southern Austria in the mid- Middle Ages - around 14 and 15th century. In Styria, there were Jewish communities in Judenburg, Leoben, Radkersburg, Voitsberg and Graz - and subject to anti-Semitic violence and expulsion from time to time. All of these places had big enough Jewish communities to support a synagogue. All Jews were finally expelled from Corinthia and Styria in 1496/1497 by Emperor Maximilian I, who was largely pressured to pursue the expulsions by Styrian landowners and minor nobles who were in debt to Jewish moneylenders. Jews were only allowed to return to Styria in the 1860s.