Why did the Indus Valley civilization come to be known as harappan civilization?

Indus civilization, also called Indus valley civilization or Harappan civilization, the earliest known urban culture of the Indian subcontinent. It was first identified in 1921 at Harappa in the Punjab region and then in 1922 at Mohenjo-daro (Mohenjodaro), near the Indus River in the Sindh (Sind) region, now both in Pakistan. Subsequently, vestiges of the civilization were found as far apart asSutkagen Dor, near the shore of the Arabian Sea 300 miles (480 km) west of Karachi, also in Pakistan, and Rupnagar, in India, at the foot of the Shimla Hills 1,000 miles (1,600 km) to the northeast.