Aureole

An aureola or aureole (diminutive of Latin aurea, "golden") is the radiance of luminous cloud which, in paintings of sacred personages, surrounds the whole figure.

In the earliest periods of Christian art it was confined to the figures of the persons of the Christian Godhead, but it was afterwards extended to the Virgin Mary and to several of the saints.

The aureola, when enveloping the whole body, generally appears oval or elliptical in form, but occasionally depicted as circular, vesica piscis, or quatrefoil. When it appears merely as a luminous disk round the head, it is called specifically a halo or nimbus, while the combination of nimbus and aureole is called a glory. The strict distinction between nimbus and aureole is not commonly maintained, and the latter term is most frequently used to denote the radiance round the heads of saints, angels or Persons of the Trinity.

This is not to be confused with the specific motif in art of the Infant Jesus appearing to be a source of light in a Nativity scene. These depictions derive directly from the accounts given by Saint Bridget of Sweden of her visions, in which she describes seeing this.

The nimbus in Christian art first appeared in the 5th century, but practically the same motif was known from several centuries earlier, in pre-Christian Hellenistic art. It is found in some Persian representations of kings and gods, and appears on coins of the Kushan kings Kanishka, Huvishka and Vasudeva, as well as on most representations of the Buddha in Greco-Buddhist art from the 1st century AD. Its use has also been traced through the Egyptians to the ancient Greeks and Romans, representations of Trajan (arch of Constantine) and Antoninus Pius (reverse of a medal) being found with it. Roman emperors were sometimes depicted wearing a radiant crown, with pointed rays intended to represent the rays of the sun. According to Islamic tradition, the Prophet Mohammed may not be depicted representationally; however some religious artists have indicated his presence in historical scenes using an empty, flaming aureole as a placeholder.

...
Wikipedia