tlatzaccan.

Headword: 
tlatzaccan.
Principal English Translation: 

at the end, at the very end

Robert Haskett and Stephanie Wood's notes from Nahuatl sessions with James Lockhart and subsequent research.

Orthographic Variants: 
tlatzacca
IPAspelling: 
tɬɑtsɑkkɑːn
Alonso de Molina: 

tlatzaccan. alcabo, alfin o ala postre.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 142r. col. 2. Thanks to Joe Campbell for providing the transcription.

çatlatzaccan. despues, ala postre, o al cabo.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, f. 15r.

Frances Karttunen: 

TLATZACCĀN at the end, conclusion, last of all / al cabo, a fin, o a la postre (M) [(3)Cf.96r,107v,131v]. The final consonant of the second syllable has lost its labiality. See TZACU(A), -CĀN.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 300.

Lockhart’s Nahuatl as Written: 

locative noun now virtually a particle. last place or time. part of set phrase çā tlatzaccān, used in effect like an adjective, last, final. tla-, tzaqua to close, -cān.
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), 239.

Attestations from sources in Spanish: 

Yc nictlalia notestamento y za tlatzaccan y za tlatzonca = Yo ago mi testamento e ultima voluntad (Ciudad de México, 1583)
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), 175.