1550s, "the plant hyacinth;" re-Greeked from jacinth (late 14c.) "hyacinth; blue cornflower," which earlier was the name of a precious stone blue (rarely red) in color (c. 1200), from Old French jacinte and Medieval Latin jacintus, ultimately from Greek hyakinthos, which is probably ultimately from a non-Indo-European Mediterranean language.
Used in ancient Greece of a blue gem, perhaps sapphire, and of a purple or deep red flower, but exactly which one is unknown (gladiolus, iris, and larkspur have been suggested). It is fabled to have sprung from the blood of Hyakinthos, Laconian youth beloved by Apollo and accidentally slain by him. The flower is said to have the letters "AI" or "AIAI" (Greek cry of grief) on its petals. The modern use in reference to a particular flowering plant genus is from 1570s. Related: Hyacinthine.