Fashion had some of its most dramatic changes in the early 20th century, as women became more active in public life; specifically, as they started participating in popular sports of the time, like riding a horse or a bike.
Stirrup pants were first worn in the 1920s by horse riders, who needed their pants to stay in place after they put on their boots. A decade later the style was adapted by skiers, who first wore them during the Winter Olympics in Germany in the '30s. Then, in the '80s, as the fitness craze swept through the United States, stirrups made a comeback — this time, as part of everyday wear. But after that, they were relegated to the "never again pile," much like, well, crunchy hairspray-ed bangs and shiny spandex and any other relics of the decade.
But stirrup pants are back again, thanks in part to — surprise! — Balenciaga, where Demna Gvesalia's whole ploy seems to be to sell us all the things we said "never again" to, at four times their original price. The weird thing is, we are kind of into them? They're a simple way to add a bit of an edge to any outfit, and there's something about putting the strap over the shoe that is just the right amount of "editorial" without looking like you're trying too hard.