Where does “гробъ” come from?
гробъ (Old Church Slavonic) comes from Proto-Slavic grǫbъ, from Proto-Slavic grěti, from Proto-Indo-European gʷʰer-, from Proto-Indo-European gʷʰe-gʷʰór-e ~ gʷʰe-gʷʰr-ḗr.
гробъ (Old Church Slavonic): grave
Ancestry of “гробъ”, step by step