Principal English Translation:
toward (Lockhart), in (see Molina); to, from, back and forth (see Karttunen and Lockhart); a certain number of times (when combined with numerals) (see Karttunen and Siméon)
Alonso de Molina:
pa. es preposicion, la qual siempre se pospone alos nombres, en esta lengua y quiere dezir, en.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 78v. col. 1. Thanks to Joe Campbell for providing the transcription.
Frances Karttunen:
-PA This indicates movement toward or from a point and, with numerals, how many times; MĀCUĪLPA 'five times'< MĀCUĪL-LI 'five.'
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 182.
Lockhart’s Nahuatl as Written:
suffixal particle. toward or from the direction of. with a numeral bound to it, times. also serves to add nuances to other relational words, to which it is suffixed.
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), 228.
Attestations from sources in English:
Auh in huel nomecauh, ocatca, ca çenca miacpa in itech, onacic, in aço çentzonpa = And many times I have sexual relations with her who was my mistress, perhaps 400 times
Bartolomé de Alva, A Guide to Confession Large and Small in the Mexican Language, 1634, eds. Barry D. Sell and John Frederick Schwaller, with Lu Ann Homza (Norman: University of Oklahoma Press, 1999), 139.
Attestations from sources in Spanish:
Auh in huel nomecauh, ocatca, ca çenca miacpa in itech, onacic, in aço çentzonpa = he pecado diuersissimas vezes con ella, que abran sido mas de quatrocientas
Bartolomé de Alva, A Guide to Confession Large and Small in the Mexican Language, 1634, eds. Barry D. Sell and John Frederick Schwaller, with Lu Ann Homza (Norman: University of Oklahoma Press, 1999), 138–139.
ceppa = una vez; oppa = dos veces; yexpa = tres veces; nappa = cuatro veces; macuilpa = cinco veces; chicuaceppa = seis veces; matlacpa = diez veces; cempoalpa = veinte veces; cempoalpa onceppa = ventiuna veces; cempoalpa omoppa = veintidós veces; cempoalpa omexpa = ventitrés veces; macuilpoalpa, cien veces, etc.
Rémi Siméon, Diccionario de la lengua náhuatl o mexicana (Mexico: Siglo XXI, 1988), xlviii.