This type of comfortable easy-chair with scrolled ears and 'mattress' seat with cushion evolved from the early 18th Century wing chair and first made its appearance in fashionable drawing-rooms in the 1750s.
Thomas Chippendale, whose Gentleman and Cabinet-Maker's Director, 1754, popularised the Louis XV style, noted in its 1763 edition that this type of 'Easy' chair or 'Chaise Longue' with elongated seat and accompanying stool was called a Peche Mortel by the French. It was also called a 'half-couch' or bergere in Messrs Ince & Mayhew's pattern book, The Universal System of Household Furniture, 1762, pl. XV.
A similar chair was sold, Simon Sainsbury: The Creation of an English Arcadia, Christie's London, 18 June 2008, lot 48.