Relish isn't just a hotdog topping. The verb relish means to enjoy something immensely. You may relish eating the relish on your hotdog, or you may relish taking an afternoon nap.
The word relish has been around since the 16th century and comes to us from the French, who are pretty good at indulging and savoring. When at a dinner party, win points with your host by sighing happily after each bite to show just how much you relish the meal. Relish is also a kind of spicy or savory condiment, the stuff you slather on hotdogs or hamburgers. So if you're fickle when it comes to pickles, you might ask them to hold the relish.