Silesian plebiscite, while the remaining former Austrian parts of Silesia were divided between Czechoslovakia and Poland. During World War II, as a result of German occupation the entire region was under control of Nazi Germany. In 1945, after World War II, most of the German-held Silesia was transferred to Polish jurisdiction by the Potsdam Agreement between the victorious Allies and became again part of Poland, although with a Soviet-installed communist regime. The small Lusatian strip west of the Oder–Neisse line, which had belonged to Silesia since 1815, became part of East Germany. As the result of the forced population shifts of 1945–48, today's inhabitants of Silesia speak the national languages of their respective countries. Previously German-speaking Lower Silesia had developed a new mixed Polish dialect and novel costumes. There is ongoing debate about whether the Silesian language should be considered a dialect of Polish or a separate language. The Lower Silesian German dialect is nearing extinction due to its speakers' expulsion. Etymology The names of Silesia in different languages most likely share their etymology— ; ; ; ; ; ; ; Latin, Spanish and English: Silesia; ; ; ; ; . The names all relate to the name of a river (now Ślęza) and mountain (Mount Ślęża) in mid-southern Silesia, which served as a place of cult for pagans before Christianization. Ślęża is listed as one of the numerous Pre-Indo-European topographic names in the region (see old European hydronymy). According to some Polonists, the name Ślęża or Ślęż is directly related to the Old Polish words ślęg or śląg , which means dampness, moisture, or humidity. They disagree with the hypothesis of an origin for the name Śląsk from the name of the Silings tribe, an etymology preferred by some German authors. In Polish common usage, "Śląsk" refers to traditionally Polish Upper Silesia and today's Silesian Voivodeship, but less to Lower Silesia, which is different from Upper Silesia in many respects as whose population was predominantly German-speaking until 1945–48. History In the fourth century BC from the south, through the Kłodzko Valley, the Celts entered Silesia, and settled around Mount Ślęża near modern Wrocław, Oława and Strzelin. Germanic Lugii tribes were first recorded within Silesia in the 1st century. West Slavs and Lechites arrived in the region around the 7th century, and by the early ninth century, their settlements had stabilized. Local West Slavs started to erect boundary structures like