Xiuhtecuhtli, whose name means "turquoise lord" in the Nahuatl language, was the Aztec "new fire" god. The Aztecs kept a "holy fire" continuously burning in the Fire Temple at Tenochtitlan ...
Another theory is that the skull-like shape is an allusion to Mictlantecuhtli, the Aztec god of the underworld, and that the Death Flute may have been used in religious practices or ceremonies.