The Aztec ritual calendar names five gods as a matched set, the Ahuiateteo, and every one of their names opens with the same number. Macuilxochitl is Five Flower. His companions are Macuilcuetzpalin, Five Lizard, Macuilcozcacuauhtli, Five Vulture, Macuiltochtli, Five Rabbit, and Macuilmalinalli, Five Grass. Each is tied to a specific day sign in the 260 day ritual calendar, the tonalpohualli, carrying the coefficient five, and it is that shared numeral, not a shared animal or plant, that makes the five a set at all.
The number itself carried a warning. In Aztec numerology five was linked to excess, the point past which a good thing, food, drink, sex, play, tips over into harm, and the Ahuiateteo were understood as the gods who preside over exactly that tipping point: not pleasure itself, which had its own patrons, but pleasure taken too far. To be born on one of their five days was considered to place a person under real risk of the vice each god oversaw.
Macuilxochitl stands at the head of the group in every surviving account, the foremost of the five rather than merely the first alphabetically or numerically. His particular excess is play: games, gambling and the music and dance that accompanied them, an association Spanish colonial sources record directly and repeatedly, and one the wider Ahuiateteo group's own logic depends on, since a set of gods personifying excess needs at least one whose vice is the one the Aztec elite themselves were most often recorded losing fortunes, freedom and occasionally their lives to.