I'm wearing (and not wearing) a real 1920s silk undergarment which, by today's standards aren't all that sexy. Back then this was considered risqué compared to the 11+ potential layers of undergarments the prior generation would don before getting dressed.

Fabrics were beginning to be mass produced, and silhouettes were changing - hence this piece looking like a loose-fitting skirt that could be slipped on under a flapper-style dress of that time.

A fun fact: there's some debate about where the term "flapper" comes from, but some derivations of the word have been around as a descriptor for women with a certain penchant for freedom from traditional mores. It was originally thought of as a derogatory term but as the movement gained popularity, propelled by women entering the workforce in droves during WW1.