one who is constant, does not get tired (see Molina)
Alonso de Molina:
amoxiuhtlatiani. constante, que no se cansa. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 5v. col. 2. Thanks to Joe Campbell for providing the transcription.