"small wooden hammer," chiefly used for driving another tool, late 14c., from Old French maillet "mallet, small wooden hammer, door-knocker," diminutive of mail, from Latin malleus "a hammer, mallet," from Proto-Italic *molalo-, *molklo- "hammer," from PIE *molkh-tlo- "crushing instrument," source also of Russian molot, Czech mlat "hammer," from PIE root *mele- "to crush, grind." It is wielded with one hand, while the heavier mall or maul requires both.

also pein, 1680s, "edged, rounded, or cone-shaped end of a hammer head," opposite the face, which is ordinarily flat; probably from a Scandinavian source (compare Norwegian dialectal penn "peen," Old Swedish pæna "beat iron thin with a hammer"). Earlier as a verb, "to beat thin with a hammer" (1510s).

"heavy knife or cutlass," used as a weapon and tool by the Spanish in the Americas, 1590s (in pseudo-Spanish form macheto), from Spanish machete "a chopping knife," probably a diminutive of macho "sledge hammer," alteration of mazo "club," which is probably [Barnhart] a dialectal variant of maza "mallet," from Vulgar Latin *mattea "war club" (see mace (n.1)). An alternative explanation traces macho to Latin marculus "a small hammer," diminutive of marcus "hammer," from a base parallel to that of Latin malleus (see mallet).

late 14c., "capable of being shaped or extended by hammering or rolling," from Old French malleable and directly from Medieval Latin malleabilis, from malleare "to beat with a hammer," from Latin malleus "hammer" (from PIE root *mele- "to crush, grind"). Figurative sense, of persons, "capable of being adapted by outside influence" is recorded from 1610s.

outermost of the three bones inside the human ear, 1660s, from Latin malleus "a hammer" (from PIE root *mele- "to crush, grind"). So called for its shape.