Where does “Gagat” come from?

Gagat (Polish) comes from Polish gagat, from Latin gagātēs, from Ancient Greek γαγάτης.

Ancestry of “Gagat”, step by step

Step	Language	Word	Meaning
1	Polish	gagat	jet
2	Latin	gagātēs	—
3	Ancient Greek	γαγάτης	—

Gagat — Etymology, Origin & Word History | Etymology Explorer