Where does “spónn” come from?

spónn (Old Norse) comes from Proto-Germanic spēnuz, from Proto-Indo-European *(s)peH-.

Ancestry of “spónn”, step by step

Step	Language	Word	Meaning
1	Proto-Germanic	spēnuz	piece of wood; chip, shaving
2	Proto-Indo-European	*(s)peH-	—