Principal English Translation: 

to come (attaches to a verb, to come doing that action)

Horacio Carochi / English: 

-tz = verb ending meaning to come
Horacio Carochi, S.J., Grammar of the Mexican language with an explanation of its adverbs (1645), translated and edited with commentary by James Lockhart, UCLA Latin American Studies Volume 89 (Stanford: Stanford University Press, UCLA Latin American Center Publications, 2001), 515 and see 164-66 n1, 166-67, 256-57.