The Discus or Disc is a motif seen in the myth of Krokus and Apollo. Apollo in his exuberance forgot that Krokus was a mortal and let the discus fly. The discus toss hurt Krokus so Apollo, in his grief, turned Krokus into a Crocus flower and out of this Discus sprouted a beautiful flower. This story is encapsulate by both the shape and flower on the Discus.

Source: Dictionary of Greek and Roman Biography and Mythology.