Where does “羊毛” come from?

羊毛 (Japanese) comes from Japanese 毛, from Middle Chinese 毛.

羊毛 (Japanese): wool, fleece

Definitions

Step	Language	Word	Meaning
1	Japanese	毛	hair, fur; a kind of unit
2	Middle Chinese	毛	—

羊毛 — Etymology, Origin & Word History | Etymology Explorer