"Popocatépetl and Iztaccíhuatl" refers to the volcanoes Popocatépetl ("the Smoking Mountain") and Iztaccíhuatl ("white woman" in Nahuatl, sometimes called the Mujer Dormida "sleeping woman" in Spanish) which overlook the Valley of Mexico and the various myths explaining their existence. The most common variety relates the Nahua romance of the princess Iztaccíhuatl and the warrior Popocatépetl. This tale is recorded in several different versions.
A summary based on one version as recounted at a September 2006 "Myth, Mortals and Immortality: Works from the Museo Soumaya de México" exhibition at the Smithsonian Institution.
Iztaccíhuatl's father sent Popocatépetl to war in Oaxaca, promising him his daughter as his wife if he returned. Iztaccíhuatl's father presumed he would not return and so arranged several suitors for his beloved daughter. When Iztaccíhuatl heard of this she killed herself with a dagger, because she knew that Popocatépetl would never survive in battle, and did not want to marry anyone else. When Popocatépetl returned, and discovered the death of his lover, he took her to the top of the mountain, hoping the cold would wake her, but instead, he froze. God covered them with snow and changed them into mountains. Iztaccíhuatl's mountain was called "La Mujer Dormida" ("The Sleeping Woman") because it bears a resemblance to a woman sleeping on her back. Popocatépetl became the volcano Popocatépetl, raining fire on the earth in blind rage at the loss of his beloved.
A different tale was told by the Nahuatl-speakers of Tetelcingo, Morelos, according to whom Iztaccíhuatl (or Istācsohuātl, as they pronounce the name) was the wife of Popo, but Xinantécatl wanted her, and he and Popocatépetl hurled rocks at each other in anger. This was the genesis of the rocky mountain ranges of the continental divide and the Trans-Mexican volcanic belt that lie between the two mountains. Finally Popocatépetl, in a burst of rage, flung an enormous chunk of ice, decapitating the Nevado de Toluca. This is why the Nevado is flat-topped, with wide shoulders but no head. Conceivably this legend preserves the memory of catastrophic eruptions. (Pittman 1954:59)