something bad or malicious (see Molina); from a- (not), cualli (good), and -yotl (having that quality, that nature)
Orthographic Variants:
aquallotl
Alonso de Molina:
aquallotl. maldad o malicia. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 7r. col. 2. Thanks to Joe Campbell for providing the transcription.