Delving back into Yours magazine's 50 Years of Fashion I learned something about the transition from corsets to girdles.
In the article "The Hidden Support" it claims that corsets were banned during World War 2, except by medical prescription. I haven't heard that before, and I have a reproduction of Make Do And Mend (which might also be in a box in my parent's shed) that mentions cleaning corsets, so it's possible that it wasn't that all corsets were banned, just that new ones weren't allowed, which does make sense as the steel used for the bones would be needed for the war effort.
After the war, in came roll ons, zip girdles and plastic boned corselettes instead, and both the article and my grandma mentioned that these were pretty uncomfortable to wear, so I figure that this must be where the idea that actual corsets are uncomfortable comes from.
The small inset article underneath mentions a few discrete things women would say to each other if they spotted that someone's petticoat was showing such as "It's snowing down south!"
I feel like it would be fun to revive that saying for Lolita wearers!