Why Does a Hiccup End with a Sudden ‘Hic’?

In Chinese, the everyday phrase for “hiccup” is often used for two different events. Belching releases gas from the stomach through the oesophagus; a hiccup is a respiratory reflex. The familiar short “hic” comes from two actions occurring in rapid succession.

First, the diaphragm and other inspiratory muscles contract suddenly and involuntarily. The chest expands and air begins to enter quickly. Almost immediately, the glottis in the larynx closes, cutting off that incoming airflow and producing the sound. The noise is not made by the diaphragm itself, nor by a bubble bursting in the stomach.

Someone may begin hiccupping after eating quickly or drinking a fizzy beverage, but that does not mean every episode has one identifiable trigger. Research commonly describes hiccups as a reflex involving incoming sensory pathways, central processing and outgoing pathways including the phrenic nerve; triggers vary, and parts of the full mechanism remain unsettled. The firm explanation should therefore stop at the observable sequence: an inspiratory spasm followed by glottal closure, rather than treating one everyday trigger as the sole cause. Brief hiccups are common; unusually persistent hiccups are a medical matter and should not be self-diagnosed from this mechanism alone.

https://medlineplus.gov/hiccups.html