the foam or froth of something that is cooked over fire (see Molina)
IPAspelling:
posoːnilloːtɬ
Alonso de Molina:
pozonillotl. espuma de cosa cozida al fuego. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 83r. col. 1. Thanks to Joe Campbell for providing the transcription.