Where does “kuna” come from?

kuna (Old Czech) comes from Proto-Slavic kuna, from Proto-Balto-Slavic kaunā́ˀ.

Ancestry of “kuna”, step by step

Step	Language	Word	Meaning
1	Proto-Slavic	kuna	marten
2	Proto-Balto-Slavic	kaunā́ˀ	—