Bell是“铃”，cat是“猫”，从字面上看就是对着猫响铃或者摇铃，它的引申义为：自告奋勇去冒险、挺身而出、替别人冒险、敢于冒险。

【例句】
It's quite difficult to get a man who can bell the cat.
很难找到危险时刻能够挺身而出的人了。

All the workers agreed that they wanted a pay raise, but nobody offered to bell the cat and talked to their boss.
所有工人都认为要加薪，但却没人自告奋勇去跟老板谈。