castanets, the percussion instrument that one holds in ones fingers and clicks while dancing (see Molina)
IPAspelling:
mɑːkɑpɑktɬi
Alonso de Molina:
macapactli. castañeta. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 50r. col. 1. Thanks to Joe Campbell for providing the transcription.