zacen.

Headword: 
zacen.
Principal English Translation: 

finally, or just this once, or as a farewell (adverb)

Orthographic Variants: 
çacen, çāçê
Alonso de Molina: 

zacen. vltimadamente, o esta sola vez, o por despedida. aduerbio.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 13v. col. 2. Thanks to Joe Campbell for providing the transcription.

Horacio Carochi / English: 

çāçê = finally
Horacio Carochi, S.J., Grammar of the Mexican language with an explanation of its adverbs (1645), translated and edited with commentary by James Lockhart, UCLA Latin American Studies Volume 89 (Stanford: Stanford University Press, UCLA Latin American Center Publications, 2001), 426–27, 499.