First attested in the Neungeomgyeong eonhae (楞嚴經諺解 / 능엄경언해), 1461, as 나ᄇᆡ(Yale: napoy). From a root *nAp meaning "flat, wide", represented in the modern language by 넓— (neol-, “wide”) (< Middle Korean nep-). Also derived from this root are 나방 (nabang, “moth”) and 넙치 (neopchi, “flatfish”). A similar derivation is seen in Chinese 蝴蝶 (húdié), see there for more.
