[babak_ap]

"Khaak" is Persian for soil, "Khaki" can mean either dust-covered or color of soil, so typically a light shade of brown in more arid regions.

[msoad]

The article says it has Hindoustani roots

It’s true that in Farsi it means earth colored as well

[babak_ap]

The article isn't wrong, it's just incomplete.

"Khaki is a loanword from Hindustani (Urdu or Hindi) ख़ाकी/خاکی 'soil-colored', which in turn comes from Persian خاک [xɒːk] khâk 'soil' + ی- (adjectival ending); it came into English via the British Indian Army."

Source: https://en.wikipedia.org/wiki/Khaki

[kranner]

Hindi/Urdu native speaker here: "khaak" means dust, not soil exactly. I believe it is the same in Farsi as well. "Khaaki" would mean 'dust-coloured'.