Where does “اُرْدُو” come from?

اُرْدُو (Hindustani) comes from Classical Persian اُرْدُو, from Proto-Turkic ordu — army, camp.

Ancestry of “اُرْدُو”, step by step

Step	Language	Word	Meaning
1	Classical Persian	اُرْدُو	—
2	Proto-Turkic	ordu	army, camp