late 14c., flowering plant (Iris germanica), also "prismatic rock crystal," from Latin iris (plural irides) "iris of the eye, iris plant, rainbow," from Greek iris (genitive iridos) "a rainbow; the lily; iris of the eye," originally "messenger of the gods," personified as the rainbow. The eye region was so called (early 15c. in English) for being the colored part; the Greek word was used of any brightly colored circle, "as that round the eyes of a peacock's tail" [Liddell & Scott].