the lower part of the cross that is driven into or stuck in the ground (see Molina)
(contains a loanword from Spanish: cruz, cross)
Alonso de Molina:
tlallampa yatica cruz. la parte baxa del madero dela cruz, que esta hincado, o metido enla tierra. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 124r. col. 1. Thanks to Joe Campbell for providing the transcription.