mochitl.

Headword: 
mochitl.
Principal English Translation: 

foam, vapor, smoke, scum; this is part of the name for tin (amochitl) and it appears in the Florentine Codex, Book 11, f. 215r., but translations vary. Digital Florentine Codex, https://florentinecodex.getty.edu/book/11/folio/215r

See also the suggestion of a type of tree in the attestations.

Attestations from sources in English: 

There is also a tree called the cuamochitl, cuauhmochitl, or guamochil, and it has edible seed pods. The origin of the term, which might help explain the "-mochitl" part remains elusive.
May N. Díaz, Tonalá (2022), 222.

Antonio Peñafiel suggests "huey mochitl" as the source, and supports the idea that the mochitl is a tree.
Nomenclatura geográfica de México (1897), 118.