Gello (), in Greek mythology, is a female demon or revenant who threatens the reproductive cycle by causing infertility, miscarriage, and infant mortality. By the Byzantine era, the () were considered a class of beings. Women believed to be under demonic possession by gelloudes might stand trial or be subjected to exorcism. Gyllou, Gylou, Gillo, or Gelu are some of its alternate forms. Etymology Gello possibly derives from Gallû, a Babylonian–Assyrian demon believed to bring sickness and death. The theory was advanced by Carl Frank (1881–1945) and supported by M.L. West, Walter Burkert, and others. The name is also preserved in the later word ghoul. Greek folk etymology links the word to the root gel-, "grin, laugh," in the sense of mocking or grimacing, like the expression often found on the face of the Gorgon, to which Barb linked demons exercising a malign influence on reproduction. Such demons are often associated with or said to come from the sea, and demonologies identify Gyllou with Abyzou, whose name is related to abyssos, the abyss or "deep." Classical Antiquity According to ancient myth, Gello was a young woman who died a virgin, and returned as a ghost (, ) to do harm to the children of others. The myth is given as an explanation of a proverb by the 2nd-century compiler Zenobius. It is noted that Sappho mentioned her, implying that Gello was a feared bane of children at least as far back as the 6th century BC. The lexicographer Hesychius who wrote in the 5th or 6th century AD but drew from earlier lexicons glossed Gello () as a ghost () who attacked both virgins and newborn babies. Since the Early Middle Ages, Gello has often been conflated with Lamia and Mormo, two similar mythological figures. Each originated as a single individual woman (with her own origin myth or aition) in Ancient Greece, but later developed into a type of frightening apparition or demon. Byzantine Period The gello eventually came to be regarded as a type of being, rather than an individual. The plural form gelloudes (), not found in Ancient Greek, came into existence in the Byzantine period, and used in the 7th–8th century by the patriarch John of Damascus, in his treatise (, "Regarding striges"). The gelloudes were considered synonymous to the () or "witches" by him, and described as beings that flew nocturnally, slipped unhindered into houses even