ἰνδικόν

Indigo comes from Greek ἰνδικόν (indikón), meaning simply 'Indian,' a neuter form of ἰνδικός (indikós, 'of India'). The full phrase was ἰνδικὸν φάρμακον (indikón phármakon, 'Indian dye'), but the adjective alone, used as a noun, was sufficient — the dye was so specifically and recognizably Indian that its geographic origin was its entire identity. The plant source, Indigofera tinctoria and related species, grew abundantly in the Indian subcontinent and had been cultivated and processed there for millennia before Greek and Roman traders encountered it. The dye arrived in the Mediterranean world as a luxury commodity, its blue so deep and so permanent compared to the woad (Isatis tinctoria) available locally that it commanded extraordinary prices. To name it 'the Indian thing' was to name what made it valuable: its foreignness, its distance, its irreproducibility in European climates.

The Romans received the Greek name as indicum and used the dye extensively, though its expense limited it to elite consumption. Pliny the Elder described indigo in his Natural History, noting its blue-purple quality and its use in painting and dyeing. The dye traveled through the Arab trade networks as the classical world contracted, and Medieval Latin preserved indicum while Arabic traders referred to it as nīlaj (also giving us 'aniline,' the synthetic dye). The Portuguese, arriving directly at the source in the late fifteenth century, disrupted centuries of overland trade: Vasco da Gama's 1498 sea route to India allowed Portuguese merchants to ship indigo directly to Europe, undercutting the Arab middlemen who had controlled the trade and flooding European markets with a dye that had previously been a rarity.

European woad-producers fought indigo's expansion aggressively. The German woad industry, centered in Thuringia, lobbied successfully for bans on indigo in several German states in the sixteenth and seventeenth centuries, with authorities declaring it 'devil's dye' (Teufelfarbe) — a designation that was commercial protectionism dressed as moral condemnation. England banned the use of indigo in 1581, though the ban was imperfectly enforced. The conflict between woad and indigo was one of the earliest trade wars in early modern Europe, fought with legislation, propaganda, and the full weight of established industry against a superior foreign product. Indigo eventually won, as better products tend to, and by the seventeenth century European markets had largely adopted it over woad.

Isaac Newton's 1666 decision to include indigo as a distinct color in his color spectrum — violet, indigo, blue, green, yellow, orange, red — gave the word scientific standing that it has held somewhat controversially ever since. Newton's choice of seven colors was influenced by a desire to match the seven notes of the musical scale and the seven classical planets; modern color scientists largely agree that indigo is not perceptually distinct from violet and deep blue in the way Newton suggested. Yet the name persists in every science classroom and in the mnemonic ROY G BIV. A color word born from a geographic label, a word that meant nothing more than 'Indian,' has been elevated to a permanent position in the scientific description of light itself.