shell [OE] The Old English scell is Germanic in origin, related to Dutch schel ‘scale, shell’ and English *scale. Use of the word as a term for an explosive projectile dates from the mid 17th century, suggested by the metal protective casing for the powder. Shell shock dates from the First World War. The notion of a shell as a place to which to withdraw (go into one’s shell) dates from the early 19th century.