Thanks for the chapter, but one small correction: that's not a pannier, it's a petticoat. A
pannier extends the
width of the skirt, so it spreads out a foot or so on either side of the wearer. A petticoat is exactly as described in the chapter, with tons of frills to add volume to the skirt. Petticoats give your skirt a nice A shape, while panniers give it an m shape.
I can't say it's a topic I've ever investigated deliberately, but isn't it more than a historic "belief", and actually backed up by rates of yeast infections for women who wear pants vs skirts?
Yep, the vagina needs to be able to "breathe" for best health. This is why the vast majority of panties have a cotton crotch section, even if they're otherwise made of other materials, like nylon, rayon, silk, etc.
How it underwear underwear if you're supposed to wear underwear under that underwear?
Because it's still worn underneath your outer layer of clothing. Coats/jackets don't count as the outer layer, since they're meant to be worn outside and taken off indoors. Women's clothing can have a great deal of undergarments, especially compared to men's. (Where it's usually underwear and a t-shirt at most.) For example for someone wearing a gothic lolita dress: panties, bra, camisole, half slip or full slip, bloomers, and petticoat. All of it serves different purposes, it's not worn for the sake of wearing it.