Why are saints drawn with halos around their heads?
The halo has been around since the time of the Greeks, and it became part of Christian art sometime in the fourth century A.D. The word “halo” comes from the Greek name for the circular threshing floor that oxen would walk on as grain was milled. The Bible does not offer any support to the idea that there are rings of light around the heads of heavenly dwellers. Artists simply use halos as way to illustrate a saint's holiness.
