1610s, "bright cloud surrounding a god," from Latin nimbus "cloud," perhaps related to nebula "cloud, mist" (see nebula). Meaning "halo" is first recorded c.1730. Meteorological sense of "a rain cloud" is from 1803.
in art, radiant circle or disk surrounding the head of a holy person, a representation of spiritual character through the symbolism of light. In Hellenistic and Roman art the sun-god Helios and Roman emperors often appear with a crown of rays. Because of its pagan origin, the form was avoided in Early Christian art, but a simple circular nimbus was adopted by Christian emperors for their official portraits. From the middle of the 4th century, Christ was also shown with this imperial attribute, as was his symbol, the Lamb of God, from the end of the 4th century. In the 5th century it was sometimes given to angels, but it was not until the 6th century that the halo became customary for the Virgin Mary and other saints. For a period during the 5th century, living persons of eminence were depicted with a square nimbus.