atlan.

Headword: 
atlan.
Principal English Translation: 

in, into, under the water
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), 211.

IPAspelling: 
ɑːtɬɑːn
Lockhart’s Nahuatl as Written: 

complex relational word. atl, -tlan
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), 211.

Attestations from sources in English: 

ça atlan in oniaque, vel aaietixque in ontetemoque = those who went down in the water got thoroughly wetted
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), 198.

Quittaque yn imicniuh yn Iancachto Onhuetzca yn atlan = they saw their friend who had fallen in the water first (late sixteenth century, Central Mexico)
Louise M. Burkhart, Before Guadalupe: The Virgin Mary in Early Colonial Nahuatl Literature, Institute for Mesoamerican Studies Monograph 13 (Albany: University at Albany, 2001), 138.

We see a pairing of atlan (water) with oztoc (cave) in the Florentine Codex as a place where the deceased go to reside. (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 6 -- Rhetoric and Moral Philosophy, No. 14, Part 7, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1961), see, for example, page 68.

auh injc onelle motlahelnelo, injc omotlaz in anetlaxoian, in atlan, in oztoc = and as if truly he had dirtied himself, had hurled himself into the bottomless pit, into the water, into a cave (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 6 -- Rhetoric and Moral Philosophy, No. 14, Part 7, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1961), 29.

ca otimotlaz in atlan, in oztoc, in tepexic = for thou hast cast thyself into the water, into the cave, from the crag (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 6 -- Rhetoric and Moral Philosophy, No. 14, Part 7, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1961), 31.