Hiccups may date back to humans’ watery ancestors. Wiring in the brain that pushes water over fish gills and makes amphibians gulp air has been imperfectly rewired in mammals. It can make the diaphragm go into spasms, which causes hiccups.
Hiccups are caused by involuntary contractions of your diaphragm — the muscle that separates your chest from your abdomen and plays an important role in breathing. This involuntary contraction causes your vocal cords to close very briefly, which produces the characteristic sound of a hiccup.
Longest attack of hiccups. Charles Osborne (1894-1991) of Anthon, Iowa, the US, started hiccupping in 1922 while attempting to weigh a hog before slaughtering it. He was unable to find a cure, and continued hiccupping until February 1990, a total of 68 years.