iztlactli.

Headword: 
iztlactli.
Principal English Translation: 

saliva, spot; poison; lie(s)

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), 222.

Orthographic Variants: 
yztlactli
IPAspelling: 
istɬɑktɬi
Alonso de Molina: 

iztlactli. baua. y tomase tambien por mentira o por ponzoña.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 49v. col. 2. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

IZTLAC-TLI saliva / baba (M), su saliva (T for possessed form) [(3)Tp. 133, 142]. By extension of meaning, this has the sense ‘poison.’
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 125.

Attestations from sources in English: 

iztlactli tenqualactli, "drool + saliva = lies;"
See Sell's comments in Bartolomé de Alva, A Guide to Confession Large and Small in the Mexican Language, 1634, eds. Barry D. Sell and John Frederick Schwaller, with Lu Ann Homza (Norman: University of Oklahoma Press, 1999), 22.

in iztlactli, in tenqualacti = the saliva, the drool (a metaphor for malicious gossip and lies)
Huehuehtlahtolli. Testimonios de la antigua palabra, ed. Librado Silva Galeana y un estudio introductorio por Miguel León-Portilla (México: Secretaría de Educación Pública, Fondo de Cultura Económica, 1991), 74–75, note 54.

Iztlactli, tenqualactli. Inin tlatolli, yehoatl quitoznequi in iztlacatiliztli, in amo neltiliztli: itechpa mitoaya in aquin tlatoani, anozo pilli, in zan muchi uel quineltoca, anozo quicaqui in iztlacatiliztli: ic iluiloya in iztlacatini: macamo iztlactli, tenqualacatili, in xiquito, in ixpan tlatoani: uel xictemo, uel xiquitta = Saliva, spittle. These words mean falsehood and untruth. It was said to the king or noble who believed all the lies he heard. "Do not tell lies or falsehoods in the presence of the king," the liar was told. "Investigate it thoroughly, look at it closely." Thelma D. Sullivan, "Nahuatl Proverbs, Conundrums, and Metaphors, Collected by Sahagún," Estudios de Cultura Náhuatl 4 (1963), 158–159.

Attestations from sources in Spanish: 

ma ticmocuitlahui in iztlactli, in tencualactli, ca amo ihuian yectli, amo ihuian cualli = cuídate del veneno, de la saliva, no es recto, no es bueno (La mentira, el engaño) (centro de México, s. XVI)
Josefina García Quintana, "Exhortación de un padre a su hijo; texto recogido por Andrés de Olmos," Estudios de Cultura Náhuatl 11 (1974), 170–171.

Auh yhuan ma ticmocitlahui in iztlactli, in tenqualacti, ca ahmo ihuiyan yectli, ahmo ihuiyan qualli = Y ten cuidado de la saliva, de la baba porque no es así recto, no es así bueno
Huehuehtlahtolli. Testimonios de la antigua palabra, ed. Librado Silva Galeana y un estudio introductorio por Miguel León-Portilla (México: Secretaría de Educación Pública, Fondo de Cultura Económica, 1991), 74–75.

themes: 
Metaphors, Proverbs, Riddles