Why do we get hiccups?
For grown-ups: the science
Hiccups happen when your diaphragm suddenly pulls in air and your vocal cords quickly close, making a hic sound.
A hiccup is an involuntary, sudden contraction of the diaphragm, followed almost immediately by closure of the glottis (the opening between the vocal cords), which interrupts the incoming air and produces the characteristic sound. Eating quickly, carbonated drinks, spicy foods, and swallowed air can be associated triggers, but the precise nerve signal that begins an episode is not fully understood. Nobody knows for sure why humans hiccup at all.
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Transcript
You are sitting after a snack, and—hic! Where did that funny little sound come from?
Below your lungs is a breathing muscle called the diaphragm. During a hiccup, it suddenly squeezes all by itself and pulls air in fast.
Almost right away, your vocal cords snap shut at the top of your windpipe. They stop that quick breath, making the hic sound.
Eating quickly or fizzy drinks may start hiccups, but nobody knows exactly how. Nobody knows for sure why our bodies hiccup at all.
So a hiccup is a quick diaphragm squeeze, then vocal cords closing. That tiny stop makes the sound!