mid-14c., "serpent's tongue" (thought to be a stinging organ), later "sharp extension of a metal blade" (1680s), from a Scandinavian source akin to Old Norse tangi "spit of land; pointed end by which a blade is driven into a handle," from Proto-Germanic *tang-, from PIE *denk- "to bite" (see tongs). Influenced in some senses by tongue (n.). Figurative sense of "a sharp taste" is first recorded mid-15c.; that of "suggestion, trace" is from 1590s. The fish (1734) so called for their spines.