cast iron (n.) Look up cast iron at
1660s, from cast "made by melting and being left to harden in a mold" (1530s), past participle adjective from cast (v.) in its sense "to throw something (in a particular way)," c. 1300, especially "form metal into a shape by pouring it molten" (1510s). From 1690s as an adjective, cast-iron.