the sole of the foot (Molina seems to put this in the possessive, first person plural)
Alonso de Molina:
toxocpal. la planta del pie. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 151r. col. 2. Thanks to Joe Campbell for providing the transcription.