a tree sap or pitch (perhaps of the type used for torches); Molina gives "tree rubber"
Orthographic Variants:
quauh ocotzotl
Alonso de Molina:
quauh ocotzotl. goma de arbol. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 86v. col. 2. Thanks to Joe Campbell for providing the transcription.