Where does “subgrave” come from?

subgrave (Spanish) comes from Spanish gravé, from Old Spanish grave, from Latin gravis, from Proto-Indo-European gʷréh₂us, from Proto-Indo-European -us — Forms adjectives from Caland system roots.

subgrave (Spanish): sub-bass

Definitions

sub-bass

Ancestry of “subgrave”, step by step

Step	Language	Word	Meaning
1	Spanish	gravé	serious, grave
2	Old Spanish	grave	—
3	Latin	gravis	heavy; troublesome, hard; grave, serious
4	Proto-Indo-European	gʷréh₂us	heavy
5	Proto-Indo-European	-us	Forms adjectives from Caland system roots

Every word from Proto-Indo-European -us →Every word from Proto-Indo-European gʷréh₂us →Every word from Latin gravis →