ceppa.

Headword: 
ceppa.
Principal English Translation: 

once, one time (see Molina, Karttunen, and Lockhart)

Orthographic Variants: 
cepa, cecpa
IPAspelling: 
seppɑ
Alonso de Molina: 

ceppa. vna vez.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 18r. col. 2. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

CEPPA once, one time / una vez (M) Z consistently has CĒPA where the other sources have CEPPA. See CEM, -PA.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 32.

Lockhart’s Nahuatl as Written: 

particle. oc ceppa, again. cē (cem) plus -pa.
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), 214.

Attestations from sources in English: 

ynic oneltic ynic aocmo zempa oncalaquizque yn intic yn calli = so that it was confirmed that never again will they [the sellers] enter the house.
Rebecca Horn, Postconquest Coyoacan: Nahua-Spanish Relations in Central Mexico, 1519–1650 (Stanford: Stanford University Press, 1997), 165, 320.

ynnic aocmo ceppa aquin tlein quitoz yn çatepan = so that no one will dispute anything again afterwards (Coyoacan, 1575)
Beyond the Codices, eds. Arthur J.O. Anderson, Frances Berdan, and James Lockhart (Los Angeles: UCLA Latin American Center, 1976), Doc. 21, 116–117.

Auh ceppa tecentlatalhuique in toiaovan in Tliliuhquitepeca, atetemoleque = Once our enemies, the people of Tliliuhquitepec and Atetemollanm had a conference about us
James Lockhart, We People Here: Nahuatl Accounts of the Conquest of Mexico, Repertorium Columbianum v. 1 (Los Angeles: UCLA Center for Medieval and Renaissance Studies, 1993), 228.

more common than cecpa (and note how ocpa can become oppa)
Frances Karttunen and James Lockhart, Nahuatl in the Middle Years: Language Contact Phenomena in Texts of the Colonial Period, Linguistics 85 (Los Angeles, University of California Publications, 1976), 101.

Attestations from sources in Spanish: 

aocmo cepa oncan tlatozque anozo tlaysnamiquizque ypampa camo intlalpan = para que no otra vez alla digan algo o contradigan ya que no es su tierra (Ciudad de México, 1570)
Luis Reyes García, Eustaquio Celestino Solís, Armando Valencia Ríos, et al, Documentos nauas de la Ciudad de México del siglo XVI (México: Centro de Investigación y Estudios Superiores en Antropología Social y Archivo General de la Nación, 1996), 119.

themes: 
Numbers, Math