1400–1800 CE Pajamas: The original paijama are loose, lightweight trousers fitted with drawstring waistbands and worn in South and West Asia by both sexes. The worldwide use of pyjamas (the word and the garment) is the result of British presence in South Asia in the 18th and 19th centuries. According to Yule and Burnell's Hobson-Jobson (1903) the word originally referred to loose trousers tied around the waist.
Such a garment is used by various persons in India e.g. by women of various classes, by Sikh men, and most by Muslim of both sexes. It was adopted from the Muslim by Europeans as an article of dishabille and of night attire ... It is probable that we English took the habit like a good many others from the Portuguese. Thus Pyrard (c. 1610) says, in speaking of Goa Hospital: "Ils ont force calsons sans quoy ne couchent iamais les Portugais des Indes" ... The word is now used in London shops. A friend furnishes the following reminiscence: "The late Mr. B—, tailor in Jermyn Street, some 40 years ago, in reply to a question why pyjammas had feet sewn on to them (as was sometimes the case with those furnished by London outfitters) answered: 'I believe, Sir, it is because of the White Ants."
According to Encyclopaedia Britannica, "They were introduced in England as lounging attire in the 17th century but soon went out of fashion. About 1870 they reappeared in the Western world as sleeping attire for men, after returning British colonials brought (them) back ...." The word "pyjama" was incorporated into the English language from Hindustani language. The word originally derives from the Persian word پايجامه Payjama meaning "leg garment."
^According to Hobson-Jobson, "The insect (Termes bellicosus of naturalists) not properly an ant, of whose destructive powers there are in India so many disagreeable experiences, and so many marvellous stories."