First attested in the Jīlín lèishì (鷄林類事 / 계림유사), 1103, as Late Old Korean寶妲 (Yale: *pòtól),[1] probably a compound of an ancient root for "daughter" *pòt- + suffix *-ól; compare Jilin leishi丫妲 (Yale: *àtól, "son"), apparently equivalent to *à(N)t- + *-ól.[2]
In the Hangul script, first attested in the Yongbi eocheonga (龍飛御天歌 / 용비어천가), 1447, as Middle Koreanᄯᆞᆯ〮 (Yale: stól). The */p-/ > /s-/ shift is difficult to explain; perhaps it simply "represents an irregular development", or perhaps the expected cluster */pt-/ had already fully merged and was realized in speech only as [t͈-], which was misanalyzed as the surface realization of the cluster /st-/.[1]