Principal English Translation:
perhaps, maybe, by chance, whether (see Molina and Lockhart)
Alonso de Molina:
at. quiza, o porventura. aduerbio.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 7v. col. 1. Thanks to Joe Campbell for providing the transcription.
Lockhart’s Nahuatl as Written:
at = particle. perhaps, whether. used especially in Tlaxcala. related to ah negative
James Lockhart, Nahuatl as Written: Lessons in Older Written Nahuatl, with Copious Examples and Texts (Stanford: Stanford University Press and UCLA Latin American Studies, 2001), 211.
Attestations from sources in English:
at timaliviz in jcnopillotl, in jcnotlacacaiotl, at vmpa onqujҫaz, at timaliviz in qujlitl, in quavitl, at toxomjz, oaҫomjz in tlalticpac = Perhaps misery, poverty will spread. Perhaps he will be destitute. Perhaps the herbs, the forest will spread; perhaps he will be in need, in want on earth (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 6 -- Rhetoric and Moral Philosophy, No. 14, Part 7, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1961), 196.
Attestations from sources in Spanish:
ynic patlahuac y aço onpohuali at noço nepa amo huel niguilnamigui = tendrá cuarenta brazas de ancho o más que no me acuerdo bien (Tlaxcala, 1609)
Vidas y bienes olvidados: Testamentos en náhuatl y castellano del siglo XVII, vol. 3, Teresa Rojas Rabiela, et al, eds. (México: CIESAS, 2002), 60–61.