According to Sir John Houlton, a veteran British administrator, the town takes its name from the small villages of Okni and Hazari – shown in old maps as Ocunhazry.

The last syllable in its name probably originated in a mango-grove, which formed a camping ground for troops and travellers marching along the ‘new military road’ from Kolkata to Varanasi, constructed in 1782 and the following years.

[1] There are ancient Cave Paintings in Isko, Hazaribagh district which are from Meso-chalcolithic period (9,000-5,000 BC).

[2] There is a group of megaliths found close to Barkagaon that is about 25 km from Hazaribagh town at Punkri Barwadih, which has been proven to date back to beyond 3000 BCE.

This significant coal deposit reserves of this district include Charhi, Kuju, Ghato Tand and Barkagaon of North Karanpura Coalfield.

Patratu and Bhurkunda was also coal mines areas of Hazaribagh but it is now in Ramgarh district.

According to the 2011 census, Hazaribagh district has a population of 1,734,495,[7] roughly equal to the nation of The Gambia[8] or the US state of Nebraska.