Where does “grao” come from?

grao (Old High German) comes from Proto-Germanic grēwaz, from Proto-Indo-European ǵʰreh₁- — to become green, grow; to grow; to green, to grow.

Ancestry of “grao”, step by step

Step	Language	Word	Meaning
1	Proto-Germanic	grēwaz	grey
2	Proto-Indo-European	ǵʰreh₁-	to become green, grow; to grow; to green, to grow

grao — Etymology, Origin & Word History | Etymology Explorer