Where does “Jaðar” come from?

Jaðar (Icelandic) comes from Old Norse jaðarr, from Proto-Germanic edaraz, from Proto-Indo-European edh-.

Ancestry of “Jaðar”, step by step

Step	Language	Word	Meaning
1	Old Norse	jaðarr	a rim, edge, selvage; the highest one, foremost...
2	Proto-Germanic	edaraz	enclosure; shelter; border, edge, rim
3	Proto-Indo-European	edh-	—

Jaðar — Etymology, Origin & Word History | Etymology Explorer