a building, perhaps a municipal council building; possibly a jail
"A puzzling word in Chimalpahin's vocabulary is 'seral,' 'selar,' or 'celar,' which refers to some institution or building on the central square of Mexico City in his time and must be a loan from Spanish. 'Seral' occurs eight times in the present corpus, 'celar' four times, and 'selar' twice. It has been proposed that 'selar,' which could conceivably be the basic form despite being the least used by Chimalpahin, is from Spanish seglar, 'secular,' and stands for the longer phrase cabildo seglar, 'secular (municipal) council,' as opposed to the cabildo eclesiástico, the ecclesiastical council...." "The word sometimes seems to refer specifically to the jail associated with the building, and it occurred to us that the origin might be Spanish cárcel, but too much omission and metathesis must be postulated to make this derivation at all likely." "The Codex Osuna, prepared in Mexico City in 1565, has an instance in which the sense seems fully developed. A Spaniard who is pictured as involved in land allocation is labeled an 'alcaldes çelar.'" In this codex, the "exact meaning of 'çelar' is left somewhat ambiguous; it could equally well mean secular' (secular alcalde) or 'municipal building' (alcalde from the municipal building) but since it does not agree in number with 'alcaldes,' it seems more likely that it is a substantive referring to the institution or the building. Freestanding load adjectives hardly existed at this time and were very rare even in Chimalpahin's time."