seems to refer to the head of the penis, perhaps peeled? Molina's term (cazporra) has yet to be translated.
tepul quaxipeuhcatl. la cazporra del miembro. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 103v. col. 1. Thanks to Joe Campbell for providing the transcription.