The term diara derives from the word diya, which means an earthen oil lamp. Diara is a word coined for a land where a diya is never lit. In local parlance in parts of Bihar, it symbolises a village located inside the embankments of the floodplains of the River Gandak in Bihar. In a wider sense, the term indicates people living in abject poverty and who face multiple vulnerabilities, due to frequent flooding of the Gandak. The river meanders and people are never sure when it would change course.

The Gandak enters India from Nepal (where it is known as Narayani or Gandaki). It flows south through seven districts of Bihar and two districts of Uttar Pradesh before joining the River Ganga at Hazipur in Bihar. More than 34 million people live in these nine districts (according to the 2011 Census), most of them in flood-prone areas.