to watch or look at what is being done (see Molina)
Alonso de Molina:
ichtaca tlachia. n. asechar mirando lo que se haze. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 32v. col. 1. Thanks to Joe Campbell for providing the transcription.