Where does “gr(b)-ti-” come from?

gr(b)-ti- (Proto-Indo-European) comes from Proto-Indo-European ger-b- — to bend.

Ancestry of “gr(b)-ti-”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	ger-b-	to bend

gr(b)-ti- — Etymology, Origin & Word History | Etymology Explorer