Uncertain. Two theories are prominent: a relation to the Germanic Silingi tribe, whose name derives from Ancient Greek Σιλίγγαι (Silíngai), itself possibly from Silesian for "swampy place." Or, from Old Polish ślęg, śląg, themselves cognate with the same Silesian source and meaning "dampness, humidity, moisture." More at Ślęża and Silesia.
- A region in central Europe, now chiefly in Poland, with small portions in the Czech Republic and Germany, from early modernity until 1945 predominantly German-speaking with Slavic-speaking minorities (and local majorities).
- Silesia (a historical region in Central Europe, shared between the Czech Republic and Poland)