pajamas (n.) Look up pajamas at
1800, pai jamahs "loose trousers tied at the waist," worn by Muslims in India and adopted by Europeans there, especially for nightwear, from Hindi pajama, probably from Persian paejamah, literally "leg clothing," from pae "leg" (from PIE root *ped- (1) "foot," see foot (n.)) + jamah "clothing." Modern spelling (U.S.) is from 1845. British spelling tends toward pyjamas.