If you're wearing a men's shirt, the buttons are usually on the right. If it's a women's shirt, they're usually on the left. The same thing can be said about zippers on jackets. But why are the buttons on different sides? Well, no one's really sure. Many historians think we do know why buttons are on the right side for men: The most common explanation is because, in ye olden times, clothing held weaponry. Chloe Chapin, a fashion historian pursuing a doctorate in the subject at Harvard University, told Today that the style can be traced back to the military. If you have a gun hidden in your shirt, it's easier to reach with the dominant hand. So if the buttons are on the right, you could theoretically slip your right hand into your shirt or jacket more easily. Before the widespread use of guns in Europe, the reason was slightly different, as Megan Garber noted in The Atlantic. Some scholars argue that it could have to do with the way men drew their swords. "A gentleman's sword was always worn on the left side, so that it could be drawn with the right hand," Paul Keers, author of "A Gentleman's Wardrobe," told The Guardian. "If a jacket buttoned right over left, the handle of the sword would be likely to catch in the jacket opening when drawn, so any serious swordsman would demand a tunic which buttoned left over right. As an indication of a masculine lifestyle, this tradition was then extended to other items of menswear. " In other words, when drawing a weapon, you would not want it to catch on your jacket or shirt. Having the buttons on the right side would eliminate this problem. But why then are women's buttons on the left hand side? According to Melanie Moore, who founded the shirt brand Elizabeth & Clarke, it could be because when buttons were invented in the 13th century, the woman wearing the shirt wasn't necessarily the person buttoning it. "Wealthy women back then did not dress themselves — their lady’s maid did," Moore told Today. "Since most people were right-handed, this made it easier for someone standing across from you to button your dress." That's the most prevalent theory, but there are a few others. One is that women held babies with their left hands, so they needed their right hand to open their shirt buttons for breastfeeding. Yet another theory is that it was fashionable for wealthy women to ride horses sideways. Having the buttons on the left would reduce the amount of airflow entering ladies' shirts, or so the argument goes. Of course, there's no real reason why fashion companies need to continue having shirt buttons on opposite sides today — it's just something they do. If you buy a new garment and the buttons are on a side you're not used it, buttoning it might feel awkward, at worst. Chances are you may not even notice. Still, for whatever reason, men's and women's shirts continue to button on opposite sides. For now at least, we'll just continue to carry these little reminders of our sartorial past on our chests.