I have always found it baffling that a woman's size is reduced to one number, as if they're all uniformly-proportioned.
I suspect it has its origins in relatively shapeless dresses.
Except "relatively shapeless dresses" have not been fashion in the west for nearly 800 years. Until relatively recently (in the grand scheme of things), clothes were not something one bought off the peg, but rather something that was made to measure by your wife, or by yourself. As fashion got more complicated and the technology evolved, printed patterns started to exist. But even here, in the first instances that was in the form of instructions on how to make a sloper. This is a fundamental building block that is used to make clothes, usually you have a skirt sloper and a bodice sloper. This would then be adapted to fit the individual. But it relied on the standardisation of a unit of measure, which really only started to happen at a national level in the 18th century.
The idea of clothes sizes has largely come about as a mixture of off the peg modernised production, and from war. Men's clothing could be relatively standardised as trousers and a shirt, that could be given to soldiers. In the napoleonic wars, the boots were not made as a left and a right, but were straight lasted in various sizes, and you would basically make your boots fit your feet by wearing them in. As the west exited the big international conflict of the 1940's, there was a mass increase in industrial clothing output, and a corresponding attempt to define sizes for people. There's some great research into this by various organisations, trying to find the average person. Only to discover it doesn't exist. So the sizes we get now are based a bit on guess work, a little bit of vitruvian man, and quite a bit of luck.
In theory a fit and healthy person should have the same ratio of chest to hips to waist. And large people are just the same ratios, but with bigger numbers. The reality is of course, that this is utter bollocks . Sizes are not standard, and noone is average, meaning that it's hard to work out what does fit.
What I don't quite get is how I can't goto a shop on say Oxford Street, or Leidseplien, I strip to my underwear and go into a booth, and it scans my body from all sides, makes a 3d model. I can then get dressed and wander into the main shop to talk to the helpful staff, who shows me on a tablet the things they have that would work well with my body shape. I can then pick the colours, and the styles, pay by card, and then 2-3 weeks later they arrive in the mail, custom made, to perfectly fit my body. The technology is all there. It just hasn't been made to happen by anyone yet...
J