tocsin (n.)

"alarm bell," 1580s, from Middle French toquassen "an alarm bell, the ringing of an alarm bell" (late 14c.), from Old Provençal tocasenh, from tocar "to strike" (from Vulgar Latin *toccare "strike a bell;" see touch (v.)) + senh "bell, bell note," from Late Latin signum "bell, ringing of a bell," in Latin "identifying mark, sign" (see sign (n.)). The current English spelling is from 1794, adopted from modern French.