When you burp, your stomach contracts and your esophagus relaxes, allowing air to expel. When you hiccup, your diaphragm contracts, and your esophagus closes up. I dunno. Kinda. I’m mock-hiccupping and burping as I type this and that seems to be what’s going on.
When all three contract, everything jams up, and that hurts.
Cool story time: Sometimes I hiccup really hard and it’s kind of painful. Thanks for coming to my TED talk