tocsin

Although it has occasionally been spelled like its homonym toxin, tocsin has nothing to do with poison. Rather, it is derived from the Middle French toquassen, which in turn comes from the Old Occitan tocasenh, and ultimately from the assumed Vulgar Latin verb toccare ("to ring a bell") and the Latin signum ("mark, sign"), which have given us, respectively, the English words touch and signal. Tocsin long referred to the ringing of church bells to signal events of importance to local villagers, including dangerous events such as attacks. Its use was eventually broadened to cover anything that signals danger or trouble.