Where does “skaþæ” come from?

skaþæ (Old Swedish) comes from Old Norse skaði, from Proto-Germanic skaþô, from Proto-Indo-European sket- — to injure.

Ancestry of “skaþæ”, step by step

Step	Language	Word	Meaning
1	Old Norse	skaði	harm, damage; loss; murder, bane, death
2	Proto-Germanic	skaþô	damage, scathe; one who causes damage; injurer
3	Proto-Indo-European	sket-	to injure

skaþæ — Etymology, Origin & Word History | Etymology Explorer