a religious holiday that is observed, a day that is "kept" (see Molina)
Alonso de Molina:
ilhuitl pieloni. fiesta de guardar. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 37v. col. 1. Thanks to Joe Campbell for providing the transcription.