According to legend, the name "Delhi" comes from a king’s terrible mistake: he uprooted a massive iron pillar, found it dripping with blood, and left his city's foundation permanently "loose."
The story centers on an 8th-century Tomara Rajput king named Anangpal Tomar. A Brahmin advised him that his kingdom would be secure only if a great iron pillar was driven deep enough into the ground to pierce the head of Vasuki, the mythical serpent king. Anangpal had the Iron Pillar of Meharauli driven down, but overcome with curiosity and doubt, he ordered it pulled back up. When the pillar was extracted, its base was wet with blood.
The Brahmin informed the king that the pillar had indeed pierced the serpent, but by uprooting it, the foundation had become loose—the word in Prakrit being dhili. The prophecy held that the Tomara dynasty's hold on the region would also remain weak. The area became known as Dhilli, which eventually evolved into Dilli and then Delhi. Inscriptions from as early as 1170 CE refer to the city as Dhillika.
Other historical theories exist. A widely cited alternative traces the name to a king named Raja Dhilu, who purportedly reigned in the region around 50 BCE and named the city after himself. The medieval historian Ferishta documented this story, though archaeological evidence of Dhilu's reign remains scarce.
Another linguistic theory points to the word dehleez, a Persian and Hindustani term meaning threshold or gateway. Geographically, the city sits on a narrow strip of land between the Aravalli hills and the Yamuna river, acting as the historic gateway between the Punjab and the fertile Gangetic plains.
Beyond myths, the economic footprint of the Tomaras provides a solid historical anchor. During their rule, the city produced widely circulated coins known as dehliwal. These coins helped cement the name across trade routes, ensuring that regardless of whether it originated from a loose pillar, an ancient king, or a geographic threshold, the name survived.