Origin and history of Injun

c. 1300 (noun and adjective), "inhabit of India or South Asia; pertaining to India," from Late Latin indianus, from India (see India).

Applied in English to the aboriginal native inhabitants of the Americas from at least 1553 as a noun (1610s as an adjective), reflecting Spanish and Portuguese use, on the mistaken notion that America was the eastern end of Asia. The English word occasionally was used 18c.-19c. of inhabitants of the Philippines and indigenous peoples of Australia and New Zealand.

The Old English adjective was Indisc, and Indish (adj.) was common in 16c.

Red Indian, to distinguish the native Americans from inhabitants of India, is attested by 1831 in British English (Carlyle) but was not commonly used in North America.

Hugh Rawson ("Wicked Words") writes that "Indian is unusual among ethnic terms for not having much pejorative value until comparatively recently." A few phrases, most of them U.S., impugn honesty or intelligence, such as Indian gift:

An Indian gift is a proverbial expression, signifying a present for which an equivalent return is expected. [Thomas Hutchinson, "History of Massachusetts Bay," 1765]

Hence Indian giver "one who gives a gift and then asks for it back" (1848). Also compare Indian summer.

Indian corn is from 1620s; to walk Indian file is from 1758. Indian club is from 1824 as a weapon, 1825 as exercise equipment (clubs were noted in Lewis & Clark, etc., as characteristic weapons of native warriors in the American West). Indian country, "land to which the Indian title has not been extinguished," is attested by 1747. Indian-head (adj.) in reference to small U.S. copper pennies with a portrait of Liberty in a native-style head-dress, is from 1862.

Indian elephant (c. 1600) is from the Asian Indian.