这是委婉语.
英文euphemism（委婉语）一词系源自希腊语.词头"eu-"的意思是"good"（好）,词干"phemism"的意思是"speech"（言语）,整个字面意义是"word of good omen"（吉言）或（好的说法）.一般认为,凡是表示禁忌或敏感事物的含蓄、迂回或动听的言词,均在委婉语之列.
英语委婉语一般可分成两大类：传统委婉语（traditional euphemisms)和文体委婉语stylistic euphemisms.所谓传统委婉语亦称是与禁忌语密切相关的.象生、病、死、葬、性、裸、拉、撒等禁忌事物,如果直接表达,那就是禁忌语,给人的感觉是粗鄙,生硬,刺耳,无礼.反之,如果间接表达,这就是委婉语,给人的印象是典雅,含蓄,中听,有礼.所谓文体委婉语,亦称实际上是恭维话、溢美之词,与禁忌语并无关系.英、美人（尤其是当代美国人）在交际过程中,为了表示礼貌,为了避免刺激,或是为了争取合作,有时会采用夸饰的手法,对一些令人不快的事物以美言相称.
Defcation (如厕）的委婉语：
to be caught short (本义）给了个冷不妨
the call of nature (本义）自然的需要
Can I add some powder?(本义）我可以茶点粉吗?
to cash(write) a check (本义）兑(开)张支票
to do a job for oneself (本义）做点私事
do one's business (本义）干自己的活
to do one's duty (本义）尽职
to ease oneself (本义）自我轻松一下
to eliminate (本义）逐出
evacuation (本义）排空
to excrete (本义）排泄
to find a haven of rest (本义）寻找安息所
to fix one's face (本义）化装
to freshen up (本义）梳洗打扮
to get some fresh air (本义）去呼吸一点新鲜空气
to give oneself ease (本义）使自己舒服一下
to go (本义）
to go into retreat (本义）去僻静
to go somewhere (本义）出去一下
to go to Egypt (本义）到埃及去
to go to one's private office (本义）到私人办公室去
to go to bathroom (本义）到洗澡间
May I adjourn?(本义）我可以变换一下地方吗?
May I please be excused?(本义）失陪了
natural necessity (本义）自然的需要
nature stop (本义）自然需要停车
to pluck a rose (本义）摘朵玫瑰
powder one's nose (本义）搽点粉
to relieve oneself (本义）轻松一下
to wash one's hands (本义）洗洗手
其它的委婉语你还可以到这个网页去看,我就不再列举.
