According to wikipedia the term "chemise" was first used to describe an outer dress from around 1780s thanks to Marie Antoinette. Before that decade a chemise was the basis of an undergarment: a very long garment in usually white cotton used to protect the skin from sweat and dirt.
Queen Marie Antoinette was known for very decorated and rich dresses. But during the second half of the 18th century she chose to wear a chemise-like piece of clothing and to be immortalized with it in 1783, by famous painter Vigée Lebrun at the Paris Salon. She was not the first to do it, as two years earlier this cloth was said to have been worn by Madame du Barry, but she was the queen and her painting became famous. From now on the garment was known by everyone as a Chemise à la Reine, aka of the Queen.
Paintings of Marie Antoinette from Vigée Lebrun and of Madame du Barry
The dress was beautiful, in a simple style but elegant and fluffy. But it was seen as an undergarment (an informal clothing) and therefore much criticized by the noble citizens of Europe. Also, it was made of cotton, a less luxurious fabric than silk. That, plus the fact that its muslin was imported in France from England and therefore the queen's choice promoted foreign industries instead of her own countries', made the critics worse. The painting, soon removed from the Salon, was also associated by most to the Petit Triannon informal meetings Marie Antoniette had with some noble friends, where she played in paesant clothing.
Unlike the shift this cloth was usually gathered with strings not only on the neckline but also on the waist and sometimes on the sleeves. It could be made of various thin fabrics such as cotton voile, muslin, crèpe, silk, lawn or linen.
In a short amount of time, despite the criticisms, it started to gain a very big popularity (by 1785 it was regarded as an acceptable everyday dress) and we can now see it in many paintings of the time. According to those drawings it was usually made in white, but it could be also coloured in light to medium shades like yellow, light blue, green and such. It could even have a matching underskirt in striped design or plain colours, some petticoat were even in a constrasting colour from the main dress.
The earliest examples of this dress were loosely gathered with strings that could be pulled or left opened, while later dresses had a fitted back with a fixed gather and also fitted sleeves. Also, it was usually worn with a sash.
A Chemise à la Reine in blue cotton
A chemise à la reine in striped fabric with fitted design.
Lady with contrasting petticoat
For Further readings about the Chemise à la Reine:
Ashelford "Colonial livery’ and the chemise à la reine, 1779–1784"
Campbell "Fashion Victims: Dress at the Court of Louis XVI and Marie-Antoinette"
Impropriety, Informality and Intimacy in Vigée Le Brun’s Marie Antoinette en Chemise