Clinking your glass against those of your drinking buddies before you all knock back shots seems a little like high-fiving, fist-bumping, or some other motion of camaraderie. And that’s pretty much what the most popular theory behind the tradition boils down to. In ancient times, people just passed around a single cup—so when that got phased out in favor of separate receptacles, tapping them together maintained that same sense of kinship.

And if you have any experience taking shots in a bar (or really just being in a bar), you may have noticed another trend: After the cheers, people often tap their glasses on the bar or table before drinking. As with regular toasts, it’s not clear exactly when, where, or why this custom began. But these days, most drinkers will cite one of two common reasons behind it. The first is slightly more morbid than you may have expected.

Dating back to ancient times, again, drinkers sometimes “poured one out”—literally poured a beverage on the ground—as a tribute to deceased comrades or loved ones who would otherwise have been there imbibing with them. As Vine Pair explains, many consider tapping your glass on the bar a modern-day, less wasteful way of doing the same thing.

If you’re not keen on thinking about loss and death every time you do a tequila shot, you might prefer the second reason for the tap: It’s simply a sign of respect to the bartender, the waitstaff, and the establishment overall. Since the toast is for your buddies and the drink itself is for you, it makes sense that you’d add in a little hat-tip to the place that made it all possible.

Those aren’t the only two explanations attached to the tradition. Some say, for example, it’s rooted in an old Irish superstition whereby tapping your glass on the table rids your drink of evil spirits. Whatever the case, your bartender will definitely appreciate a tap much more than a full drink dumped on the floor.

[h/t Vine Pair]