The baseball uniform has always been an imperfect marriage of tradition and functionality. Early apparel was made of wool, which wasn’t ideal for chasing after baseballs in the searing heat of summer, for example. But one relic of the sport's old-school days remains: the stirrup.

This secondary strapped sock that wraps around a player’s foot is almost like baseball formal attire, and some players still sport them today. But where did they come from, and what’s the purpose?

In the mid-1800s, ballplayers were prone to wearing uniforms that had pants extending all the way to the top of the shoe. Then, in 1868, the players of the Cincinnati Red Stockings decided to make a fashion statement by hiking their pants up to just under the knees, knickers-style. Other teams followed suit in the belief that a shapely calf might excite female fans attending the game. (Remember, this was the 1800s.)

NSFW: The nearly pornographic Cincinnati Red Stockings of 1868.Wikimedia Commons // Public Domain

This move exposed their over-the-calf socks, which created a bit of a health problem. In those days, the toxic dye used in colored uniform socks could potentially run into the open leg wounds players often got after being “spiked” by an opponent's cleats. That, coupled with any dirt or bacteria, could prompt a fatal infection. (This was, of course, before antibiotics.)

In 1905, player Nap Lajoie of the Cleveland Naps got a serious infection believed to be from the dye getting into a cut, confirming those fears. Players began wearing white socks underneath their uniform sock, creating a double-sock scenario. The inner layer was dubbed a sanitary sock because it offered a measure of protection against germs and didn’t contain any of the harmful dyes.

While this solved one problem—death by cleats—it created another. If you’ve ever tried to wear two socks, you know there’s a problem fitting into your shoes. To get the dual-sock effect while still being able to don footwear, stirrups were implemented. The sanitary sock covered the entire foot, while the second sock covered the lower leg and was secured in place by a strap under the heel.

A new baseball tradition was suddenly afoot.

Players still wear stirrups today.Rich Schultz/Getty Images

Stirrups became a part of the uniform, enduring the advent of penicillin and other milestones. They were so low to the foot that most people couldn’t see them, but players eventually began opting for a variety of styles, like stripes. In 1936, the Boston Red Sox (who else?) debuted an iconic broad-stripe design, which was emulated by other teams.

By the 1980s, the choices were numerous. Players started pulling the stirrups taut, creating a “high cut” look. Some players pull their pants back down; some keep the high socks without the stirrups; some just have the stirrup sewn in to create the arched look. Others sport them on certain days or games or for special occasions.

The next time you’re at a game and see a pair of stirrups, you can thank the Cincinnati Red Stockings and their formidable calves.

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