the roundness of a buckler or target, or of a round table, etc. (see Molina)
Alonso de Molina:
malacachiuhcayotl. redondez de rodela o de mesa redonda. &c. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 51v. col. 1. Thanks to Joe Campbell for providing the transcription.