Michael Psellos
Numerous early Byzantine amulets (6th to 7th century label its demon as "Abyzou" identifiable with Obyzouth, a demon that strangles newborns according to the 1st to 3rd century Greek text called the "Testament of Solomon". This Abyzou (Obyzouth) has been equated with the Gello (Gyllou), albeit in later literature, for example, the writings of Michael Psellos of the 11th century.