the.com/cold chisel

means A tough, unhardened-edge steel chisel driven with hammer blows to cut or split cold metal, rather than metal softened by heating in a forge.

from Named in plain contrast to the blacksmith's hot chisel, which sliced through iron heated soft and glowing in the forge. The 'cold' chisel does the harder job: biting into metal at room temperature, so its edge must be tempered tougher and its user more patient, letting hammer and steel wear the metal down by force rather than fire.