a quarter of a mutton, or a quarter pound of bread, or a piece of quince (see Molina)
IPAspelling:
sennɑkɑstɬi
Alonso de Molina:
cennacaztli. vn quarto de carnero, o vn quarteron de pan, ovn cacho de membrillo. &c. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 17r. col. 2. Thanks to Joe Campbell for providing the transcription.