iron bomb
/ˌʌɪən ˈbɒm/noun
1A thick-walled iron container used to hold material for chemical or physical experimentation at high pressure. Now rare.
2Originally: an explosive bomb with an iron casing. Later: (Military ) a conventional air-dropped bomb, as opposed to a smart bomb or a nuclear bomb.
Origin
Mid 18th century; earliest use found in Benjamin Martin (bap. 1705, d. 1782), lecturer on science and maker of scientific instruments. From iron + bomb.