structural:reformatting, stylistic:tone
Toponym

There are a number of myths and legends associated with the origin of the name Delhi. One of them is derived from Dhillu or Dilu, a king who built a city at this location in 50 BCE and named it after himself. Another legend holds that the name of the city is based on the Prakrit word dhili (loose) and that it was used by the Tomaras to refer to the city because the iron pillar of Delhi had a weak foundation and had to be moved. According to Panjab Notes and Queries, the name of the city at the time of King Prithviraj was dilpat, and that dilpat and dilli are probably derived from the old Hindi word dil meaning "eminence". The former director of the Archaeological Survey of India, Alexander Cunningham, mentioned that dilli later became dihli/dehli. Some suggest the coins in circulation in the region under the Tomaras were called dehliwal. According to the Bhavishya Purana, King Prithiviraja of Indraprastha built a new fort in the modern-day Purana Qila area for the convenience of all four castes in his kingdom. He ordered the construction of a gateway to the fort and later named the fort dehali. Some historians believe that Dhilli or Dhillika is the original name for the city while others believe the name could be a corruption of the Hindustani words dehleez or dehali —both terms meaning "threshold" or "gateway"—and symbolic of the city as a gateway to the Gangetic Plain.

The people of Delhi are referred to as Delhiites or Dilliwalas. The city is referenced in various idioms of the Northern Indo-Aryan languages. Examples include:

The form Delhi, spelled in the Latin script with the h following the l, originated under colonial rule and is an alternation of the spelling based on the Urdu name of the city (دہلی, Dehli).