ayauhcalli (Mdz64r)
This iconographic element shows a building in profile open to the viewer's left. Its t-shaped beams in the doorway are painted turquoise. The building itself, very reminiscent of a calli, is white. Along the top, horizontal plane of the building, there are three pairs of vertical dashes, seemingly representing mist or fog [ayauh(tli)] and these are also painted turquoise (the color of water).
Stephanie Wood
The gloss explains that this is an "ayauhcalli," or fog-house. The gloss also describes it as a mezquita, which was the Spaniards' early term for a teocalli, religious house, drawing from their experience with the religious temples of the Moors in the Reconquest of Iberia. The term ayauhcalli combines ayauh(tli) (fog) with cal(li) (house or building).
The markings on the top of the building are somewhat reminiscent of mist, which is akin to rain quiyahuitl or quiahuitl. See below, right. Another explanation for the particular shape of these paired hash marks (what Dehouve calls the double-stroke sign) might have something to do with the "hua" of possession, perhaps providing a phonetic indicator for ayauhui. (See below, right, for other "hua" suggestions). The t-shaped entrance to the building, which usually has terracotta-colored wooden beams, here has turquoise beams. The choice of color certainly seems to relate to water, again, and therefore to preciosity and a religious significance.
Elena Mazzetto has studied the ahuacalli sanctuaries in detail, and shows how they relate to religious festivals, which have a calendrical connection (veintenas).
Stephanie Wood
mezquita non[-]
brada ayauhcali
mezquita nombrada ayauhcalli
Stephanie Wood
c. 1541, or by 1553 at the latest
Stephanie Wood, Xitlali Torres
temples, templos, houses, buildings, architecture, religious structures, religious buildings, religious festivals, casas, edificios, arquitectura, santuarios, calendario, fiestas, double-strike sign, double-stroke sign

a(tl), water, https://nahuatl.wired-humanities.org/content/atl
ayauh(tli), fog, mist, https://nahuatl.wired-humanities.org/content/ayahuitl
quiahui(tl), to rain, https://nahuatl.wired-humanities.org/content/quiahuitl
cal(li), house or buiding, https://nahuatl.wired-humanities.org/content/calli
teocal(li), temple or church, https://nahuatl.wired-humanities.org/content/teocalli
la casa de la niebla
Stephanie Wood
Codex Mendoza, folio 64 recto, https://digital.bodleian.ox.ac.uk/objects/2fea788e-2aa2-4f08-b6d9-648c00..., image 138 of 188.
Original manuscript is held by the Bodleian Libraries, University of Oxford, MS. Arch. Selden. A. 1; used here with the UK Creative Commons, “Attribution-NonCommercial-ShareAlike 3.0 License” (CC-BY-NC-SA 3.0)