Where does “castañas” come from?

castañas (Spanish) comes from Old Spanish castanna, from Latin castanea, from Ancient Greek καστάνεια, from Ancient Greek κᾰ́στᾰνᾰ — sweet chestnuts; chestnut.

Ancestry of “castañas”, step by step

Step	Language	Word	Meaning
1	Old Spanish	castanna	chestnut
2	Latin	castanea	a chestnut tree; a chestnut
3	Ancient Greek	καστάνεια	Alternative form of κᾰ́στᾰνᾰ; chestnut
4	Ancient Greek	κᾰ́στᾰνᾰ	sweet chestnuts; chestnut

Every word from Ancient Greek κᾰ́στᾰνᾰ →Every word from Ancient Greek καστάνεια →Every word from Latin castanea →