Where does “побережжя” come from?

побережжя (Ukrainian) comes from Ukrainian берег, from Old East Slavic берегъ, 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.

Ancestry of “побережжя”, step by step

StepLanguageWordMeaning
1Ukrainianберегbank, shore, coast, beach
2Old East Slavicберегъbank; shore
3Proto-Slavicbergъhill; slope, cliff?; bank, shore?, coast?
4Proto-Balto-Slavic*bérgashill
5Proto-Indo-European*bʰérǵʰoshill
6Proto-Indo-Europeanbʰerǵʰ-to rise; high, lofty; hill, mountain
Every word from Proto-Indo-European bʰerǵʰ- →Every word from Proto-Indo-European *bʰérǵʰos →Every word from Proto-Balto-Slavic *bérgas →