The name yum cimil and the nine levels come from colonial sources
Resonance
The dying the bereaved death workers
Symbols
SkullSkeletal faceBonesOwlThe day sign cimi
Mythology Summary
Ah Puch, the rotten one, is the Maya death god, called Yum Cimil, Lord of Death, in the colonial Yucatec sources; in the codices he is the skeletal God A of the Schellhas classification, with a fleshless face, a distended belly and ornaments of bone, and he is the ruler of Mitnal, the lowest of the nine levels of the underworld in the colonial Yucatec account. Much of what is said about those nine levels and about the name Yum Cimil comes from Diego de Landa and the Yucatec dictionaries rather than from the pre-Conquest codices, and the entry keeps that distinction. He is a death god of the Maya pantheon, not a demon.
Modern Practice
Ah Puch is worked by those who sit with the dying, in the burial and in the food set out for the dead that the Yucatec communities still keep. The habit of folding him into the Mexican Day of the Dead as though the two were one tradition is a modern flattening.