someone without ability, or someone who does things backwards (see Molina)
Alonso de Molina:
aoompatzi. inabil, o el que haze la cosa al reues. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 6v. col. 2. Thanks to Joe Campbell for providing the transcription.