In preparing for the next exhibit, I needed to do a little research on lady's undergarments, or, unmentionables; as one did not mention these under-garments outside the dressmaker's establishment or within one's dressing room; much less in polite company! There is a great deal of history available on undergarments dating back to the wrap of the Egyptians. That, however, is a little too far back for this exhibit, which will be women's fashions from 1800-1900, with a few unmentionables included.
So, why were undergarments created? There are several answers to this - changing a woman's shape, modesty and hygiene. Prior to the very late 1780's early 1790's the wearing of long skirts, a couple of petticoats, a linen chemise and corset were all that women thought necessary; or even cared to wear. Heavy quilted petticoats and pannier skirts were not only attractive, the heavy fabrics provided warmth for the lower half of the body. Unlike the Empire/Regency fabrics, these heavier fabrics did not "blow up" if the wind was gusty.
(Photograph: 1770's Gown Courtesy of "Jane of All Trades,"
With advent of the turn of the century and fashion shift to the Empire/Regency style, things changed. With the advent of the 19th century approaching, finer, lighter fabrics; even sheer fabrics, replaced the heavier 1700's fabrics. Lawn, sheer silks, batiste and organza suited the long, flowing Empire/Regency styles. However, they also revealed more detail of a woman's lower anatomy. For that reason, women of the Empire/Regency era began wearing undergarments to cover their "nether regions."
In the portrait to the left (1805 as shown by this Gérard portrait of Mme. de Staël) you can see the more easily discerned shape of Madame de Staël's body than that of a woman wearing the 1700's heavier gowns.
Known as "pantaloons," these early garments covered a portion of the breasts and would go to either just below the knee or to the ankle. Pantaloons were already being worn by men. Made of light stockinette (a loosely knitted stretch fabric [now used for some bandaging]), women's pantaloons were also flesh-toned; tending to make it look like the lady was wearing no undergarments at all. (Scandalous!)
From the 1820's onward, pantaloons became pantalettes, or sometimes knickers. Pantalettes and knickers were a more feminine product made of cotton, often with ornate decoration such as pin-tucks and lace. Fastened at the waist with a split (unsewn, open) crotch. The difference between pantalettes and knickers is that pantalettes
had a narrower leg with gathering for fullness in the seat area. Knickers were much roomier (wider in the leg and seat) and shorter in length. Moving away from heavier cottons, these garments were made from batiste or a fine lawn fabric.
Over the pantalettes would be a chemise, as you see in the photographs to the left. The corset would then be tight tightly over the chemise to be followed by a hoop and then starched petticoats; and finally, the outer garment to be worn.
The "combination" in this photograph dates to the later 1800's. Combination garments were worn from the 1870's onward (think "Teddy"). In the photograph to your right, you see an 1800's-1900 combination with a corset cover bodice. The corset would
be tied tightly over the combination, then the corset cover tied closed over the corset. Numerous starched petticoats would be followed by a bustle-pad, bustle and finally a skirt or other outer garment. Punto Tagliato, or cut-work lace (eyelet) was developed in Italy from the 14th - 16th centuries. You see lovely samples of this in both the combination pantalettes and corset cover.
 Oklahoma Embroidery Supply and Design, "Embroidery 101: Cutwork. Copyrighted 2017. 3/18/2017. https://www.embroideryonline.com/t-Embroidery101_CutworkEmbroidery.aspx
For further reading about 17th and 18th century undergarments:
http://www.fashion-era.com/drawers-pants-combinations-knickers-fashion.htm#The Need for Nether Region Underwear