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.

Black Toddler & Girls Dance Shorts – Leotard Boutique

Ladies Teigan Full Coverage Briefs, Black – BLOCH Dance US

Capezio Dance Brief - Adult and Child Sizes - Black – Dance Irish

Girls Team Basic High Waist Dance Shorts by Capezio : TB131C Capezio , On Stage Dancewear, Capezio Authorized Dealer.

ORINERY Cotton Girls Underwear Hipster Dance Briefs Assorted Hipster Panties Soft Toddler Kids Undies 6-Pack : : Clothing, Shoes

Energetiks High Cut Brief Adult

Girls Dance Shorts Bike Short For Underdress 8-10 Years Black 6 Pack

Ladies Teigan Full Coverage Briefs, Black – BLOCH Dance UK

Girls' High-Waisted Modern Dance/Jazz Shorts - Black STAREVER

Kids Invisible High Cut Dance Brief

Baltogs Dancewear

Adult & Kids Dance Shorts, Dance Briefs

Sugar & Bruno Bloomer Shorts - Black

Women's contemporary jazz shorts, panties