brežje (Serbo-Croatian) comes from Serbo-Croatian brijȇg, from Proto-Slavic bergъ, from Proto-Balto-Slavic *bérgas, from Proto-Indo-European *bʰérǵʰos, from Proto-Indo-European bʰerǵʰ- — to rise; high, lofty; hill, mountain.
brežje (Serbo-Croatian): hills