Black Dance Briefs, Girls Dance Briefs

Black Dance Briefs have been around for ages. They are used by dancers to protect their thighs from the chafing caused by garter belts. [based on a comment from the original post.
Dance brief with flat lock stitch detail.Nylon spandex.

KUKOME Ballet Dance Underwear High Cut Cotton Dance Briefs Shorts for Women Girls : : Clothing, Shoes & Accessories

Mondor V-Waist Tactel Dance Short Adult 3549L – Dance Essentials Inc.

OVIGILY Child Black Dance Briefs Jazz Cut Girls Spandex Ballet Dance Briefs Lycra Mid Waist Cheer Briefs Workout Underwear Kids

Dancer Shorts & Leggings in Kids Sizes

Dance Shorts & Briefs - Inspirations Dancewear Canada

Adult's Classic Stretch Dance Brief

Studio 7 Dancewear, Performance Briefs

Girls Underwear Ballet Dance, Ballerinas Wear Underwear

Team Cheerleading/Dance Briefs – Athletic Apparel

BLOCH Ladies Dance Pants Briefs Knickers High Deep Waistband Black