lilac: [17] Like the river Nile, the lilac gets its name from its colour. The Sanskrit word for ‘dark blue’ was nīla. This passed into Persian as nīl, from which was derived nīlak ‘bluish’. This developed a variant līlak, which English acquired via Arabic līlak, Spanish lilac, and early modern French lilac. Along the way it was applied to a shrub of the genus Syringa, on account of its mauve flowers. [lilac etymology, lilac origin, 英语词源]