Sonipat name is derived from the word Sonpat which means in Sanskrit language the suvarna prastha (gold place). One popular tradition avers that it is one of the five patas or prasthas (Indraprastha, Panipat, Talpat, Bhaghpat and Sonipat) mentioned in the Mahabharata which Yudhishthira demanded from Duryodhana. Another tradition ascribes its foundation to Raja Soni, thirteenth descent from Arjuna, a brother of Yudhishthira.

There has never been any doubt regarding the antiquity of the district. The region has yielded pottery of pre-Harappan, late-Harappan, Painted Grey Ware, early historical, Northern Black Polished Ware and early medieval times showing thereby that parts of the district were inhabited by different people, some of these parts show continuity while in others there is a break. The evidence so far available archaeological as well as literary – is quite meager even to provide any clear outline of the historical growth of the district during the early phases.

The pre-Harappans were the earliest people inhabiting the district. The next important phase in the pre-history of the region is marked by the advent of the people using Painted Grey Ware and generally associated with the Aryans. The earliest literary reference to Sonipat is, of course, in the Paniniya Ashtadhyayi where it has been mentioned along with other towns whose names end in prastha (Sonaprastha).