to protect someone from the sun and rain with a kind of shield (see Molina)
IPAspelling:
tʃiːmɑllɑpɑtʃoɑ
Alonso de Molina:
chimallapachoa. nino. (pret. oninochimallapacho.) lo mesmo es que chimalcaltia. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 21r. col. 1. Thanks to Joe Campbell for providing the transcription.