A chaise longue is an upholstered sofa in the shape of a chair that is long enough to support the legs of the sitter. In modern French, the term chaise longue can refer to any long reclining chair such as a deckchair. A literal translation in English is "long chair". The term chaise lounge, used since (1800) is a corruption of the French chaise longue "long chair," with the French word order; the second word is confused in English with lounge.

Source: Wikipedia