To protect their outer wear (gowns, day dresses, etc.) from sweat and body oils, women of the Regency era wore shifts or chemises. These were simple garments, much like a man of today might wear an undershirt to protect his dress shirt or a woman might wear a “teddy” to protect her blouse. Chemises and shifts were made of cotton, but women who could afford the cost would choose something more luxurious – something like silk. Thin and tightly woven, the shift was smooth to the touch. This type of cotton actually cost more than silk did. These cotton shifts lasted longer than did the silk ones. There is some speculation that part of the duties of a lady’s maid was to make certain the shift did not bunch up.

The chemise became popular in Europe in the Middle Ages. Women wore shifts/chemises under their gowns, while men wore them with their trousers or braies to be covered with doublets, robes, etc. A chemise was the only underwear worn by women by the end of the Regency Period. Although women did not wash their outer garments after each use, they did wash the shifts/chemises regularly. Washing was harsh on the clothing. Shifts and chemises were dried in the sun so that the sun would bleach the fabric, but those dyed had a tendency to fade. Those in charge of the laundry would hang the dyed garments in the shade after they turned the item inside out to help prevent fading. 

“Men’s chemises may be said to have survived as the common T-shirt, which still serves as an undergarment. The chemise also morphed into the smock-frock, a garment worn by English laborers until the early 20th century. Its loose cut and wide sleeves were well adapted to heavy labor. The name smock is nowadays still used for military combat jackets in the UK, whereas in the Belgian army the term has been corrupted to smoke-vest.

“A chemise, shift, or smock was usually sewn at home, by the women of a household. It was assembled from rectangles and triangles cut from one piece of cloth so as to leave no waste. The poor would wear skimpy chemises pieced from a narrow piece of rough cloth; while the rich might have voluminous chemises pieced from thin, smooth fine linen.” (Chemise)

That being said, during the winter, the Victorians were known to wear flannel or wool pantalets, under petticoats and stockings but the chemise remained cotton. 

https://en.wikipedia.org/wiki/Ell

Cloth was measured in ells. “An ell (from Old Germanic *alinâ cognate with Latin ulna) is a unit of measurement, originally a cubit, i.e., approximating the length of a man’s arm from the elbow (“elbow” means the bend or bow of the ell or arm) to the tip of the middle finger, or about 18 inches (457 mm); in later usage, any of several longer units. In English-speaking countries, these included (until the 19th century) the Flemish ell (³⁄₄ of a yard), English ell (⁵⁄₄ yard) and French ell (⁶⁄₄ yard), some of which are thought to derive from a “double ell”. Several national forms existed, with different lengths, including the Scottish ell (≈37 inches or 94 centimetres), the Flemish ell [el] (≈27 in or 68.6 cm), the French ell [aune](≈54 in or 137.2 cm) the Polish ell (≈31 in or 78.7 cm), the Danish ell (≈25 in or 63.5 cm), the Swedish aln (2 Swedish fot ≈59 cm) and the German ell [elle] (Hamburg, Frankfurt, Cologne, Leipzig: 57,9 cm)

“Select customs were observed by English importers of Dutch textiles: although all cloths were bought by the Flemish ell, linen was sold by the English ell, but tapestry was sold by the Flemish ell. In England, the ell was usually 45 in (1.143 m), or a yard and a quarter. It was mainly used in the tailoring business but is now obsolete. Although the exact length was never defined in English law, standards were kept; the brass ell examined at the Exchequer by Graham in the 1740s had been in use ‘since the time of Queen Elizabeth.'” (Ell)

By the mid 1850s, dresses had 7-9 yards of material, and so it became common practice to disassemble the dress – bodice from skirt, sleeves from bodice – easier to wash & quicker to dry. Afterward, the pieces were reassembled. 

1660s stays with sleeves http://www.marquise. de/en/themes/korsett/ korsett.shtml

The word corset did not come into use until the 19th Century. Before that time, people used the words bodice or stays. In French 18th century texts (e.g. Garsault, Diderot), one may find the term corset as referring to a lightly stiffened bodice with tie-on sleeves, whereas proper stays are called corps. Until the 17th Century, the custom was to stiffen the bodice of the dress rather than to have a separate corset. 

http://www.elizabethancostume.net/corsets/history.html

“The first and best known example of a 16th century corset is the German pair of bodies buried with Pfaltzgrafin Dorothea Sabine von Neuberg in 1598. This corset is shown in detail on page 47 and 112-113 of Janet Arnold’s Patterns of Fashion 1560-1620 and in Jutta Zander-Seidel’s book Textiler Hausrat. It is made of three layers of cream-colored fabric, the outer layer being silk backed with linen and the inner lining of linen, and has channels backstitched between the two layers into which whalebone was inserted. It has tabs at the waist, as well as small eyelets at the waistline through which the farthingale (stiffened hoop skirt) or petticoat could be fastened to the corset.” (History of the Corset)

Costume Parisians, 1808-9, “Hair in braids, Corset a la Ninon.” This corset laces in back is and much more “structural,” clearly attempting to increase the bust and draw in the waist. Unlike Victorian corsets, this one doesn’t seem focused on drawing in the natural waist, an unnecessary feature when fashions have the waist under the bust. Notice that no effort is made to move the breasts together–the two breasts very separated was fashionable. Later corsets that even more clearly divide the breasts were called “divorce corsets.” The Underwear Page http://regencyfashion. org/dress/und.html

The Robe á l’Allemand, a the stiff bodice, survived until about 1730 in England. Stays are conical in shape, and they press “the breast up and together, with tabs over the hips. The tabs are formed by cuts from the lower edge up to the waistline that spread when the stays are worn, giving the hips room. They prevent the waistband of the skirt from crawling under the stays, and the waistline of the stays from digging into the flesh.

“There are stays that lace at the back (Diderot calls them corps fermé, closed stays) and those that lace across a stiff stomacher in front (corps ouvert, or open stays). Examples that lace both back and front (but not over a stomacher) are quite rare. Stays that lace in front only are even rarer and so far only known to me from the region of Southern Germany. In all these cases, spiral lacing is used. Although 18th century stays were not meant to be seen, they are often quite decorative, with finely stitched tunnels for the boning, precious silk brocade and possibly gold trim. 

“The basic shape of stays didn’t change the whole century long. Towards the end, around 1790, when dress waists begin to wander upwards, the stays become slightly shorter. Since paniers were not worn anymore, the skirt is supported by small pads sewn to the tabs. At the same time, physicians made themselves heard, warning against the harm done by tight-lacing. While lacing wasn’t usually overdone as much as one century later, it often started earlier: It started with tightly wrapping babies and included children’s corsets, forcing the still soft skeleton into a fashionable shape.” (A Short History of the Corset)

As the 19th Century turned, the corset changed somewhat to match the empire line of the gowns worn by the fashionable set.Frankly, clothes were not so form fitting as in previous decades. The newer style allowed for a woman’s gaining weight or for her pregnancy. Therefore, it was no longer necessary to define the waistline, but it was still in fashion to lift the breasts higher (but with a definite separation). Cups were used for the first time as part of the stays/corsets. The busk, which was used in the early 17th Century to keep the front of the stays straight, returned to keep the cups separated. 

“Since slender figures could keep the bust in shape with the help of only a firm bodice lining, it is mainly stout and over-endowed ones who wear corsets or short stays which already looked like early bras. Therefore, not many corsets from that time have been preserved. Unlike the earlier ones, they tend to be plain and functional. Maybe the fact that they contained less boning led people to refer to them by the (French) term for lightly boned bodices, corset. This is just a theory, but it would explain why the earlier term corps/stays had been replaced with corset by the 1820s.” (A Short History of the Corset)

In the late 1820s, the fashion again accentuated the waist; therefore a need for a corset returned. Stitched in grommets for laced eyelets on corsets were replaced by hammered-in metal eyelets in the late 1820s. This was followed by the planchet, which is two metal strips that are designed to hook together so the woman could open the corset from the front without unlacing it. “This busk, as it is called in English, makes it possible to change the lacing completely: Both ends of the cord are threaded through the eyelets crosswise and knotted together at the end. At waist level, one loop is formed on either side and used to pull the lacing tight. This kind of lacing is still used today.” (A Short History of the Corset)

The hourglass figure we think of when corsets are the subject became more prominent by the mid 1800s. “From about 1860, when some patterns have caught on, more emphasis is placed on beautiful fabrics and elegant lines again. From the years around 1870-90, a large number of meticulously made corsets has been preserved, partially embroidered and with satin top fabric in various of colours.

Until c. 1870, the crinoline hid anything from the waist down, so corsets ended not much below the waist. Later, dresses closely hug the figure at least in front, so corsets become longer. This development reached a peak around 1880, when the fashionable silhouette hugged the hips on all sides. The belly is tamed, but not flattened, by a new kind of busk: The pear-shaped spoon busk (see right corset in the picture above) bends inwards to compress the stomach region, then outwards over the belly, an in again over the lower abdomen. If laced tightly, a spoon busk forces the soft bits (i.e. fat as well as inner organs) downwards – and during the 1890s, tight-lacing becomes so popular that physicians sound the alarm again.” (A Short History of the Corset)

Women did not want the stays cutting into the skin. In cool weather, the chemise and stays were additional layers to keep the female warm. With layers of natural fibers, shifts repel the perspiration, called “glistening” at the time.