The Greek term baioulos (βαΐουλος) was used in the Byzantine Empire to refer to a preceptor or tutor. Although it clearly derives from the Latin term baiulus ("bearer"), in the 12th century the theologian Theodore Balsamon claimed that it came from baion (palm leaf) because the preceptor was charged with supervising the growth of young minds.
In the 9th century, Theophanes the Confessor used the term to refer to the emperor's personal preceptor. In the 10th century, the title megas baioulos (μέγας βαΐουλος, "grand preceptor") was created for Basil Lekapenos, tutor of the future Romanos II. Pseudo-Kodinos, writing after the middle of the 14th century, did not know where the megas baioulos fell in the Byzantine hierarchy, but other contemporary lists of offices, such as the appendix to the Hexabiblos and the verse list of Matthew Blastares, which reflected the usage under Andronikos II Palaiologos (r. 1282–1328) or during the reign of Andronikos III Palaiologos (r. 1328–1341), place him in the 18th place, after the parakoimomenos tou koitonos and before the kouropalates.