to be in heat (speaking of a female dog) (see Molina)
Alonso de Molina:
moquetzallani. (pret. omoquetzallan) estar cachonda la perra. &c. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 060r. col. 1. Thanks to Joe Campbell for providing the transcription.