Principal English Translation: 

(an ending for transitive verbs)

Horacio Carochi / English: 

-a = (ending of transitive verbs)
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), 225 n4, 234–35, 246–47 with n2, 496.

Attestations from sources in English: 

As explained in Carochi, transitive verbs ending in -a take -ltia in the causative and become -i in the applicative.