tencuahuitl.

Headword: 
tencuahuitl.
Principal English Translation: 

a man with a bad tongue (see Molina); one with wooden lips, or someone who cannot be refuted (Sahagún)

Orthographic Variants: 
tenquauitl, tenquahuitl
Alonso de Molina: 

tenquauitl. hombre de mala lengua.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 99v. col. 1. Thanks to Joe Campbell for providing the transcription.

Attestations from sources in English: 

Tenquauitl. Itechpa mitoa: intlatol chicaoac, in auel tenpanauilo, in amo tlatolpanauiloni = Wooden lips. This is said about someone whose words are not firm. He cannot be refuted, no one can over-ride him in words.
Thelma D. Sullivan, "Nahuatl Proverbs, Conundrums, and Metaphors, Collected by Sahagún," Estudios de Cultura Náhuatl 4 (1963), 100–101.

themes: 
Anatomy
Metaphors, Proverbs, Riddles
Speech, Speaking, Oral Tradition