17c. spelling change of indico (1550s), "blue powder obtained from certain plants and used as a dye," from Spanish indico, Portuguese endego, and Dutch (via Portuguese) indigo, all from Latin indicum "indigo," from Greek indikon "blue dye from India," literally "Indian (substance)," neuter of indikos "Indian," from India (see India).

Replaced Middle English ynde (late 13c., from Old French inde "indigo; blue, violet" (13c.), from Latin indicum). Earlier name in Mediterranean languages was annil, anil (see aniline). As "the color of indigo" from 1620s. As the name of the violet-blue color of the spectrum, 1704 (Newton).

metallic element, 1864, Modern Latin, from indicum "indigo" (see indigo) + chemical name element -ium. So called for its spectral lines. Ferdinand Reich (1799-1882), professor of physics at Freiberg, isolated it while analyzing local zinc ores in 1863 and identified it as a new element by the two dark blue lines in its spectrum, which did not correspond to any known element. The discovery had to be observed by his assistant, Theodor Richter, because Reich was color-blind.

late 13c., "blue, bluish-gray," later "rich, dark blue; purplish-black," from Old French pers "(dark) blue, livid; wan, pale," from Late Latin persus, perhaps a back-formation from one of the early European forms of Persia. Compare indigo, from India.

chemical base used in making colorful dyes, 1843, coined 1841 by German chemist Carl Julius Fritzsche and adopted by Hofmann, ultimately from Portuguese anil "the indigo shrub," from Arabic an-nil "the indigo," assimilated from al-nil (with Arabic definite article al-), from Persian nila, ultimately from Sanskrit nili "indigo," from nilah "dark blue."

With suffix -ine indicating "derived substance" (see -ine (1); also see -ine (2) for the later, more precise, use of the suffix in chemistry). Discovered in 1826 in indigo and at first called crystallin; it became commercially important in 1856 when mauve dye was made from it. As an adjective from 1860.

West Indian shrub from which indigo is made, 1580s, from French or Portuguese anil "the indigo shrub," from Arabic an-nil "the indigo," assimilated from al-nil, from Persian nila, ultimately from Sanskrit nili "indigo," from nilah "dark blue."

1690s, capital of the Philippines, said to be from Tagalog may "there is" + nila "shrub of the indigo family," but this last element would not be a native word. It gave its name (with altered spelling) to manilla hemp (1814), the original source of manilla paper (1832); see manilla (1). 

"of, belonging to, or native to Tyre," Phoenician island-city in the Levant, 1510s, from Latin Tyrius "of Tyre," (Latin Tyrus), island-city in the Levant, from Greek Tyros, from Hebrew/Phoenician tzor, literally "rock, rocky place."

Especially in reference to Tyrian purple, a dye chemically similar to indigo, made there in ancient times from certain mollusks (Murex brandaris).

plant formerly much cultivated for the blue dye extracted from its fermented leaves, also the dye itself; Middle English wode, from Old English wad "woad," also the blue dye made from its leaves, from Proto-Germanic *waidīn, which is perhaps cognate with Latin vitrium "glass" (see vitreous). Boutkan considers it a substratum word. The dye with which the ancient Britons painted themselves blue, it has since been superseded commercially by indigo.

Germanic cognates include Danish vaid, Old Frisian wed, Middle Dutch wede, Dutch wede, Old High German weit, German Waid "woad." Middle English also had the word as waide, via Anglo-French or directly from the Old North French form. French guède, Italian guado are considered Germanic loan-words.