Hiccups (or Hicoughs) - as everyone knows - are semi-persistent, regular involuntary contractions (technically known as myoclonic jerks) of the diaphragm. immediately followed by laryngeal closure.
They can be brought-on by a wide range of triggers - e.g. eating spicy foods etc. etc.. (Although almost always benign, they can also be a symptom of some diseases.)
Hiccups are so common that they are considered to be an in-built evolutionary trait - in other words presumably having some use in our evolutionary past.
There are a number of theories as how hiccups might have evolved, for example :
Further technical reading The Patho-physiology of Hiccups - aComprehensive Review IJSDR , Volume 6 Issue 7.
( Note that there are a number of drugs used to relieve hiccups - but they have unknown mechanisms of action. e.g. Lacosamideplugin-autotooltip__plain plugin-autotooltip_bigLacosamide
Lacosamide - sold under the brand name Vimpat and others - was discovered at the University of Houston in 1996. It was licenced in Europe and the US in 2008 for the treatment of partial-onset seizures in Epilepsy.
"Its precise mechanism of action was unknown at the time of approval, and the exact amino acid targets involved remain uncertain to this day." )