DERA, a word of Persian extraction, has several connotations. The original Persian word derah or dirah means a tent, camp, abode, house or habitation. In current usage in rural Punjab, a farmhouse or a group of farmhouses built away from the village proper is called dera. Even after such an habitation develops into a separate village or a town, it may continue to be called dera, e.g. Dera Bassi in Patiala district of the Punjab, or Dera Ghazi Khan and Dera Isma`il Khan in Pakistan. Where colloquially used in place of Hindi dehara, the word will carry the connotation of a temple or memorial over a cremation site.

The examples are Dera Sahib Gurdwara at Lahore and Dera Baba Nanak, a town in Gurdaspur district of the Punjab. In a different but not totally unrelated sense, dera is apparently derived from the Persian dair meaning a monastery or convent. Monasteries, hermitages or seminaries set up by religious persons are almost invariably called deras. They, too, are usually at some distance from the nearest village or town, and have an exclusively male population. For example, Daudhar Dera. Among Sikhs, Nirmalas and Udasis have their deras spread throughout the countryside.

Although the Guru Granth Sahib is installed in most of them, their custodians prefer to call them deras rather than gurdwaras. In Sikh times, the word dera was also used for army camps or cantonments to particularize regiments or armies commanded by different generals, such as Derah Ghorcharha Khas Sham Singh Atarivala, Derah Ramgarhian, Derah Naulakkha and Derah Imam udDin. In the Guru Granth Sahib dera is used to mean abode or living place, permanent rather than temporary (GG, 256), and also in the sense of a camp or citadel (GG, 628).

References :

1. Fauja Singh, Military System of the Sikhs. Delhi, 1964
2. Cunningham.J.D., A History of the Sikhs. London, 1849