What are they?
They are small shaped pads, primarily made out of pure cotton that fit over the underarm seam of sleeved dresses. The purpose is two-fold; firstly to increase comfort, providing a smooth cushion under the arm, followed by the more practical application of absorbing perspiration, hence the choice of pure cotton for its excellent absorbent properties.
Back in the days when couture dressmaking was in its heyday, cutting down on dry cleaning bills was the principal reason for their use, as all couture dresses by nature were dry-clean only. Today, this principle is no less true and still makes sound practical sense as prolonged dry cleaning shortens the life of a garment.