hi atomic, hiccup (hikhik) is normally due to the sudden and involunatry contraction of diaphrama and intercostal muscles( muscles in between the ribs and this contraction is released of certain nerves specially N. phrenicus and intercostal nerves.This contraction forces us to inhale but at the same time glottis get closed and produces this short and sharp sound like hik.
Etilogy: embryological reasons (i don know much about it)
External factors(noxa): alcohol abuse, cold drink, hectic swallowing , hot food, stress, excitement etc.
Therapy: pathological disorders may last for more than a year. Normal hiccups can be stopped by taking piece of dry bread (for e.g.)or ice,diverting mind, holding ur breath after deep inspiration.In fright, flight and fight hiccups stop automatically.
.This is all what i know.Hope i could help u.

astu: