Why/When did the act of women shaving their legs/armpits start? I can't seem to find a clear answer on Google.

I know it's now a social norm in most parts of the world but I find it odd that men aren't as much expected to do the same. Kind of like how women wear pants and skirts, but men only wear pants. Who knows though... maybe in 100 years men will be the ones wearing skirts and shaving their legs, while women are hairier.