A euphemism for
diarrhea suffered by
tourists to
Mexico, after
drinking the local water or eating foods they are not used to. The phrase is sometimes used for other parts of Latin America, and regional variations exist (e.g. in India, Gandhi's Revenge).
Montezuma was Emperor of Mexico from 1502 to 1520. In 1520 he died, a prisoner of the Spanish conquistador Cortez. The phrase alludes to the extinguishment of indigenous peoples following colonization, and their getting back at the colonizers (or their progeny, as the case may be).
It makes light of the plight of any indigenous people who have faced colonization and met similar ends, as if upset stomach could be compared to genocide.
Monetzuma's Revenge is also a video game, released for the Colecovision and other consoles in the mid-1980's. It belongs to the Pitfall genre of games. The main character, Panama Joe, must collect as many treasures as possible while avoiding traps.