cepan.

Headword: 
cepan.
Principal English Translation: 

together, together with, in company of one another, altogether

Orthographic Variants: 
çepan
IPAspelling: 
seːpɑn
Alonso de Molina: 

cepan. juntamente, o en compañia.
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: 

CĒPAN together / juntamente, o en compañia (M), significa simultaneidad o concomitancia (R) This is abundantly attested in B and C with the first vowel marked long. B also has two attestations in which the vowel is specifically marked short. CĒPAN can be incorporated into verbs to convey the sense of simultaneity. T has CĒPAYEHU(I) ‘ to be the same age ‘ which seems to be derived from CĒPAN. The YEHU(I) element suggests a derivation from the verb YĀ but it has regular rather than suppletive causative and nonactive forms. R has CEHCĒPANOĀ ‘to unite things.’ See CĒ, -PĀN. CĒPAYEHU(I) See CĒPAN.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 32.

Attestations from sources in Spanish: 

yquac yaque sepanolestin yn içepan mexica opan Florida = entonces fueron los españoles, junto con los mexicas, a la Florida. (Tlaxcala, 1662–1692)
Juan Buenaventura Zapata y Mendoza, Historia cronológica de la Noble Ciudad de Tlaxcala, transcripción paleográfica, traducción, presentación y notas por Luis Reyes García y Andrea Martínez Baracs (Tlaxcala y México: Universidad Autónoma de Tlaxcala, Secretaría de Extensión Universitaria y Difusión Cultural, y Centro de Investigaciones y Estudios Superiores en Antropología Social, 1995), 158–159.