Ideas:

1. Possibly this type of glyph is showing 'one-leg', a well-known mythological figure in ancient times. He is called 'Hunrakán' (= one leg) by the Maya indians.

2. "From it [Hunrakán] comes our 'hurricane', so there is no wonder that he disposes of wind, rain, thunder and lightning in lavish amounts. But he is not for all that a mere weather god, since he is one aspect of Tezcatlipoca himself, and the true original One-Leg that looks down from the sky..." (Hamlet's Mill)

Tezcatlipoca is the dark opponent of the light (Sungod) Quetzalcoatl and perhaps we therefore should think of him as Saturn. If so, then it is understandable that Saturn implies darkness and wetness (cfr Hb9-54). The week seems to have two poles: Sun's day and Saturn's day, white and black.