First attested in the Gugeupganibang eonhae (救急簡易方諺解 / 구급간이방언해), 1489, as Middle Korean ᄇᆞᆰ〯쥐〮 (Yale: pǒlk-cwúy). Shift from earlier 밝쥐 (bakjwi), itself a compound of 밝 (bak-, “bright”, probably implying “bright-eyed”) + 쥐 (jwi, “rat”). In the past, Korean people thought bats had bright eyes because they did not know that they could fly in dark caves using ultrasound. 
- (SK Standard/Seoul) IPA(key): [ˈpa̠(ː)k̚t͡ɕ͈ɥi] ~ [ˈpa̠(ː)k̚t͡ɕ͈y]
- Phonetic hangul: [박(ː)쮜]
- Though still prescriptive in Standard Korean, most speakers in both Koreas no longer distinguish vowel length.
|Revised Romanization (translit.)?||bagjwi|
- (archaic): 밝쥐 (bakjwi, “literally, “bright (eyed) rat””)
- 편복(蝙蝠) (pyeonbok)
- (literally): 두더지 (dudeoji, “mole”)