Where does “грузовой” come from?

грузовой (Russian) comes from Russian груз, from Proto-Slavic grǫzъ, from Proto-Slavic gręzti, from Proto-Balto-Slavic grimz-.

Ancestry of “грузовой”, step by step

Step	Language	Word	Meaning
1	Russian	груз	weight, burden, load; cargo, freight, lading
2	Proto-Slavic	grǫzъ
3	Proto-Slavic	gręzti	to sink
4	Proto-Balto-Slavic	grimz-	—

грузовой — Etymology, Origin & Word History | Etymology Explorer