From the series "Myths about the colors":: iris

The name of the flower received from the hands of the famous healer Hippocrates, who gave the name to the plant after the Greek goddess iris, proclaiming to the people the will of the Olympian gods. Goddess Irida went over the rainbow to earth, so the word "iris" in Greek means rainbow.
When the Titan Prometheus stole the heavenly fire Olympus and gave it to people on earth broke out a marvelous semisodium rainbow - so great was the joy of all living things on earth. The sunset is already gone and the day faded, and the sun is gone, and the rainbow still shone over the world, giving people hope. It is not extinguished until dawn. And when morning returned to his place the sun, where glowed and shimmered with the colors of the rainbow, blooming irises,...