брег (Russian) comes from Old East Slavic брѣгъ, from Old Church Slavonic брѣгъ, 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.
брег (Russian): bank, shore, coast