khaki: [19] Khaki is part of the large linguistic legacy of British rule in India. In Urdu khākī means ‘dusty’, and is a derivative of the noun khāk ‘dust’ (a word of Persian origin). It seems first to have been used with reference to the colour of military uniforms in the Guide Corps of the Indian army in the late 1840s. The term followed the colour when it was more widely adopted by the British army for camouflage purposes during the South African wars at the end of the 19th century. [khaki etymology, khaki origin, 英语词源]
"dust-colored cloth," 1857, from Urdu khaki, literally "dusty," from khak "dust," from Persian. First introduced in uniforms of British cavalry in India (the Guide Corps, 1846); widely adopted for camouflage purposes in the Boer Wars (1899-1902). As an adjective from 1863. Related: Khakis.