something liquid, or something long lying down on something else (see Molina)
Alonso de Molina:
ipan tlatectli. cosa liquida, o cosa larga echada sobre otra cosa. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 42r. col. 1. Thanks to Joe Campbell for providing the transcription.