十八世纪爱尔兰政客Sir Boyle Roche常常发表惊人的言论，例如：Half the lies our opponents tell about me are not true! （那些攻击我的谎言，十有四五都是无中生有！）当时人们笑他失言，就说：He has put his foot in his mouth again.
Put one’s foot in one’s mouth直译的话是“把自己的脚放进自己的嘴里”，为什么它的意思却是“说错话”呢？原来这个成语是从另一个成语put one’s foot in it衍生出来的。Put one’s foot in it本来是指一不小心一脚踩在污水或比污水更加厉害的东西上面，现在英国人也直接用这个成语来表达“说错话”。put one’s foot in one’s mouth就是一不小心一脚踩在自己的嘴巴上了，也就是说错话，美国人更习惯这种用法。
Longman Dictionary of Contemporary English对put one’s foot in it / put one’s foot in one’s mouth的解释是这样的：to say something wrong or unsuitable, as a result of thoughtlessness, and so cause an awkward situation.
例如：
I really put my foot in my mouth when I asked him how his wife was; she’s left him for another man.
（我真的不该多嘴去问他他的妻子怎样，她已经离开他而跟另一个男人去了。）
