early 14c., plural of quoyn, from Old French cooin (Modern French coing), from Vulgar Latin codoneum, from Latin cotoneum malum "quince fruit," probably a variant of cydonium malum, from Greek kydonion malon "apple of Kydonia" (modern Khania), ancient seaport city in Crete.
The plant is native to Persia, Anatolia, and Greece; the Greeks imported grafts for their native plants from a superior strain in Crete, hence the name. Kodu- also was the Lydian name for the fruit. Italian cotogno, German Quitte, etc. all are ultimately from the Greek word.