Indigo is the name of a purplish-blue color which comes from the color of a dye extracted from plants exported from India to the Ancient Greeks and Romans, who viewed it as a luxury product. That’s where the origin of the name comes from, from Ancient Greek indikon meaning “Indian dye”; India is named from the Indus River, one of the longest rivers in Asia. To the Ancient Greeks, it was known as Indus/Indos while the name became India to the Romans. Its name derives from Sanskrit Sindhu meaning “river, stream; flood, waters; sea, ocean”, which either comes from Proto-Indo-Iranian or a PIE root word.
Origin: uncertain, either PII or PIE