ca.

ca. ni. (pret. onicatca.) estar, o ser.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 10r. col. 2. Thanks to Joe Campbell for providing the transcription.

ca. porque. conjunction para dar razon de algo.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 10r. col. 2. Thanks to Joe Campbell for providing the transcription.

CA. Corresponding to the English construction 'as for (something)', followed by a clause, Nahuatl has '(something), CA followed by the relevant clause. C gives the example inōn calli, ca àmo tè mocal 'as for that house; it is not yours'. The CA is not obligatory to the construction; its presence conveys emphasis. CA also combines as initial element with other particles and particle clusters; CA AHMŌ (emphatic negation), CA HUEL OC 'todavia', CA NEL 'porque', CA NEL NOZO 'porque' (emphatic), CA YE 'ya', CA ZAN 'sino que', etc. The emphatic force of CA is often negligible.

ca = introductory, emphatic, and causal particle
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), 68-69, 405 n7, 498.