Nightclothes and nightgowns first appeared as a loose-fitting cloth, full length unisex. Their creation was done in the 18th century, the negligee took the form of a lounging garment for women, while long loose pants and long loose shirt called Pyjamas replaced long gowns for men. Pyjies were designed after harem pants from Iran, that is why the word is composed of Iranian words. Pae: means leg in Persian and Jama means clothing.
Some theories suggest that the word comes from the Hindi language, during the reign of Briton in India. They were introduced to the British civilization in the 17th century.