Lyle Campbell and Terrence Kaufman discuss the presence of words for "metal" among the Olmecs.
Lyle Campbell and Terrence Kaufman, "A Linguistic Look at the Olmecs," American Antiquity 41, no. 1 (January 1976): 85
(22) Axe (human sacrifice?): PMZ *pus to cut with a knife or axe, *pusan metal (axe?) . . . —Nuhua pus-teki, to cut, *te-pos-(tli) axe, metal (literally te- 'someone' plus -pos 'cut', or "people cutter"); Pokom pos stone war axe ax pos 'wonder worker', pus 'witch' (encantador); Cakchiquel pos polished stone; Quiché pos, pus 'to sacrifice men by removing their hearts', to cut, polished stone, magic power; Cakchiquel and Quiché *pus-nawal* 'magic power, witch'; Huave apəš to chop with axe (hachear); Proto-Central Otomian *bes-na metal, lead; Proto-Popolocan *pos hard stone. From these examples it seems certain that terms for "axe" were widely borrowed from MZ, and probably its ritual significance was borrowed as well.