tlahmati = to jest, to practice trickery and deception; or, to be quick-witted (see Karttunen and Molina)
tlamati = to know something; to know magic
(It is not clear that these are separate words. To "know something" and "to know magic" are both definitions--among others--that are given for tlamati in the Gran Diccionario Nahuatl. The suggestions of deception, trickery, and magic may be evidence of a European friars' filter entering into some of the translations.)
See the Nahuatl hieroglyphs for the name Tlamauh (often glossed as Tlamao) as they appear in the Visual Lexicon. The use of the stellar or starry eye suggests a special type of knowledge that is gained through seeing--along the lines suggested by Marc Thouvenot: "Mientras que imati se relaciona con un conocimiento empírico dado po la experiencia a través del ojo, mati hace referencia a un saber interno, abstracto, dado por la capacidad de pensar."