Stories We Like: A Guide to the Comma
1520s, "electric ray," from Latin torpedo, originally "numbness" (from the effect of being jolted by the ray's electric discharges), from torpere "be numb" (see torpor). The sense of "explosive device used to blow up enemy ships" is first recorded 1776, as a floating mine; the self-propelled version is from 1860s.
1873, from torpedo (n.). Figurative sense attested from 1895. Related: Torpedoed; torpedoing.