The Collaborative International Dictionary
Chemisette \Chem`i*sette"\, n. [F., dim. of chemise.] An under-garment, worn by women, usually covering the neck, shoulders, and breast.
Wiktionary
n. An item of women’s clothing, popular in the 1860s and 1870s, worn to fill in the front and neckline of any garment.
Wikipedia
A chemisette (from French, "little chemise") is an article of women's clothing worn to fill in the front and neckline of any garment. Chemisettes give the appearance of a blouse or shirt worn under the outer garment without adding bulk at the waist or upper arm.
Chemisettes of linen or cotton were often worn with day dresses in the mid-19th century, and could be decorated with tucks, embroidery (especially whitework), or lace.
When wide pagoda sleeves were fashionable (1850s), chemisettes might have matching engageantes (false undersleeves).
Usage examples of "chemisette".
The long sleeves were gathered at the wrist and the neckline was filled in with a modest, pleated chemisette Harriet had pinned a fresh white lace cap on her untamed hair.
He called her "my wife", tutoyed* her, asked for her of everyone, looked for her everywhere, and often he dragged her into the yards, where he could be seen from far between the trees, putting his arm around her waist, and walking half-bending over her, ruffling the chemisette of her bodice with his head.
The full, pleated skirt would flow nicely around her legs as she moved, and the laced bodice over the white voile chemisette might draw the eye even of a president no longer young.
She followed numbly, barefooted and shivering in her chemisette and pantaloons.