tlancotoni.

Headword: 
tlancotoni.
Principal English Translation: 

to lose a tooth; for a child to slough off the baby teeth; for teeth to break off (see Molina and Sahagún)

IPAspelling: 
tɬɑnkotoːni
Alonso de Molina: 

tlancotoni. ni. (pret. onitlancoton.) caerse me algun diente, o mudar el muchacho los dientes.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 127v. col. 1. Thanks to Joe Campbell for providing the transcription.

Attestations from sources in English: 

nitlancotoni = I break my teeth (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 10 -- The People, No. 14, Part 11, 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), 109.

themes: 
Anatomy
Children, Childhood, Adolescence