ahuatl.

Headword: 
ahuatl.
Principal English Translation: 

a thorn; a hairy worm; a caterpillar; (vowel length is important for distinguishing these meanings from the meaning oak tree; see Karttunen and Molina)

IPAspelling: 
ɑhwɑtɬ
Alonso de Molina: 

auatl. enzina, roble, gusano lanudo. o espina.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 9r. col. 2. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

AHHUA-TL long, slender thorn / espina (M), espina delgada (C) M puts the definition of this together with the definitions of ĀHUA-TL ´oak´and ĀHUĀ-TL, a type of caterpillar
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 5.

Attestations from sources in English: 

Oc izca cencamatl, in ma iuh haoatl, in ma iuhquj vitztli, in ma iuhquj itztic ehecatl = Behold, here is yet a word like a thorn, like a spine, like a biting wind (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 6 -- Rhetoric and Moral Philosophy, No. 14, Part 7, 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: 
Animals, Bugs, Insects, Reptiles, Fish, etc.