tecuancoatl.

Headword: 
tecuancoatl.
Principal English Translation: 

a poisonous snake or serpent (see Molina)

Orthographic Variants: 
tequan coatl, tecuan coatl
Alonso de Molina: 

tequan coatl. biuora o serpiente ponzoñosa.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 104v. col. 2. Thanks to Joe Campbell for providing the transcription.

Attestations from sources in English: 

auh in ma çan yuhqui tequan, coatl oquipotz, oquiztlacmin, oquicocolizcuiti = It is just as if a poisonous snake spewed out and shot poison at them and made them sick
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), 141.

Attestations from sources in Spanish: 

auh in ma çan yuhqui tequan, coatl oquipotz, oquiztlacmin, oquicocolizcuiti = quedó toda como herida, y emponçoñada del mortifero veneno de la Serpiente
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), 140–141.