The metaphorical Source of the electronic equivalent of a poiSoned-pen letter. Derived from EngliSh metaphorS of the form "pen dipped in X" (where X = e.g. "acid", "bile", "vitriol"). TheSe map over neatly to thiS hackiSh uSage (the curSor being what moveS, leaving letterS behind, when one iS compoSing on-line). "Talk about a naStygram! He muSt' ve had hiS curSor dipped in acid when he wrote that one!" [Jargon File] (1996-12-27)