a horse muzzle or chin strap (see Molina)
(partly a Spanish loanword, caballo, horse)
Orthographic Variants:
yecamecayo cauallo
Alonso de Molina:
yecamecayo cauallo. barboquejo o bozal de cauallo. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 34v. col. 1. Thanks to Joe Campbell for providing the transcription.