tapachtli.

Headword: 
tapachtli.
Principal English Translation: 

sea shell, coral (see Karttunen); reddish in color

Orthographic Variants: 
tapachtli
IPAspelling: 
tɑpɑtʃtɬi
Alonso de Molina: 

tapachtli. coral, concha o venera.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 90v. col. 2. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

TAPACH-TLI sea shell, coral / coral, concha, o venera (M), concha (del mar) (Z) [(2)Zp.32,212]
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 214.

Attestations from sources in English: 

Tapach nocallin = My house is of coral
John F. Schwaller, "The Pre-Hispanic Poetics of Sahagún's Psalmodia christiana," in Psalms in the Early Modern World, eds. Linda Phyllis Austern, Kari Boyd McBride, and David L. Orvis (London: Ashgate, 2011), 326.

themes: 
Colors
Marine, Maritime, Lacustrine
Shells