toc·sin 
(tŏksĭn)
(tŏksĭn)n.
1.
a. An alarm sounded on a bell.
b. A bell used to sound an alarm.
2. A warning; an omen.
[French, alteration of toquassen, from Old French touque-sain, from Old Provençal tocasenh : tocar, to strike (from Vulgar Latin *toccāre) + senh, bell (from Late Latin signum, from Latin, signal; see SIGN).]