What's in a name? Not much in most mobile games. You simply pick something that tickles your fancy and fits the character limit and away you go. Maybe it's a screen name you use on other gaming platforms, but even in multiplayer affairs, it doesn't make much difference.
At first glance, the same would appear to hold true for slither.io. After all, you can change your nickname after every game if you want, and for such a simple game, plenty of people use their nickname as a joke, a political statement, or both.