Where does “gref” come from?

gref (Middle English) comes from Old French grief, from Late Latin grevis, from Latin gravis, from Proto-Indo-European gʷréh₂us, from Proto-Indo-European -us — Forms adjectives from Caland system roots.

Ancestry of “gref”, step by step

Step	Language	Word	Meaning
1	Old French	grief	pain; anguish; suffering; sad
2	Late Latin	grevis	—
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 →