A hiccup is the result of a nervous disorder, and the offending nerves that have been implicated are vagus and phrenic nerves. Both of these nerves are located in the throat near the epiglottis and, in simple terms, a short circuit in them is the cause of a hiccup. There are other nerves that do play a part in the disorder as well.
The explanation and treatment for a continuous session of hiccups requires some details. A hiccup, as mentioned earlier, is a nervous disorder. Therefore, a hiccup can last for a few minutes or even continue for years. The world record for the longest hiccup was set by a Charles Osborne who suffered from a case of hiccups for 68 years. Contrary to some beliefs, a hiccup is not cause by eating or drinking incorrectly; though sometimes, the improper ingestion of food can irritate the vagus nerve. The vagus nerve is actually quite infamous for some of its vagaries. A little bit pressure on this nerve can actually render one unconscious for a few minutes and that little bit of pressure can be something as benign as not chewing properly and swallowing too fast.
This was the case of a famous president who was rendered unconscious for a few minutes after eating a pretzel. There is also a theory that a hiccup is a vestigial reflex that we practice since our days as an embryo. The evolutionary theory behind this state is that at the earliest stage of our lives, the human embryo is similar to an amphibian and the same reflex is practiced as we start to adapt from gills to lungs. This is in fact the reason that babies that are premature hiccup so much since they are not adapted yet to working with their lungs. This same reflex is sometimes activated in an adult human as well.
For really serious cases of hiccups, drugs are sometimes administered like anti-spasmodics, sedatives and even anti-psychotic drugs. This is because the nervous system has to be dulled down to a level where the patient is either unconscious or extremely lethargic. This dulling down calms the nervous system and the hiccups disappear. Some of the anecdotal evidence like holding ones breath and saying the Lord’s Prayer backwards corroborate the fact that a distraction would bring one out of a session of hiccups. The most effective thing that you can do during a case of hiccups is not concentrate on it, judge is timings and when it is about to happen, yawn artificially. This will create a shock to the system making you forget about the hiccup.