?What does the name Delhi (Dehli) mean

It can mean a city with a defensive shield:

ढाल n. DhAla shield

The city’s mythical and old names, ie. Indrapat (protected by the god of war) and Purana Qila (Old Fort) indicate this:

पातुम् {पा} infinit. pAtum {pA} to protect

The Persian term Dehli is “far away” (dur ast), in fact, is Dehli drvu sta, ie. Dehli is standing firm:

ध्रुव adj. dhruva stable

ध्रुव adj. dhruva fixed