俚语 “throw somebody under the bus”是什么意思？

今天信手从报纸堆里翻出一张两个月前的老报纸，温故知新，读到一位女读者 Peggy 的来信，题目是：Bush already threw us under the bus

现摘录几句她的“反动”言论：
Regarding " Obama will throw us under bus " (June 7, Letters): We are already under the bus and were put there by President Bush and Dick Cheney and all their old men friends. Bush has put us in a very deep hole financially and we have lost our standing in the rest of  the world……

Peggy 女士反复用到throw somebody under the bus, 照字面意义是把某人扔到巴士底下。而根据上下文应是对目前总统竞选的看法和对现任政府的不满，与公交车有什么联系呢？

本笔者孤陋寡闻，不知其喻义，多亏了网络的发达，google 后终于搞清其相应的中文意义。

throw somebody under the bus… 拿某人当牺牲品／替罪羊，背叛／出卖某人

用于指一个人为了保护自己而牺牲或出卖別人的情况，也可用于向领导打小报告，说某个人的不是，或是公开批评某个人，使人下不了台，等小人行为。

Ok，各位明白了上面读者来信中的throw somebody under the bus 的意义了吧？我就不多言了，莫谈政治。  

那么为什么用throw somebody under the bus来表示“把某人当牺牲品”？麻烦诸位看官耐心参考下文，问题将迎刃而解。摘自word-detective.com

Dear Word Detective: What is the origin of the phrase “to throw one under the bus”? — Brenda Varney.

Good question, and, it would seem, a timely one as well. It’s hard to pick up a newspaper or turn on the TV these days without hearing of someone being “thrown under the bus.” Last year CNN’s Jack Cafferty declared that “Rather than face Senate confirmation hearings over his reappointment as the Chairman of the Joint Chiefs of Staff, the Bush White House has decided to simply throw General Peter Pace under the bus.”

Elsewhere, the E-Commerce News warned that a new song royalty scheme would “… throw large webcasters under the bus and put an end to small webcasters’ hopes of one day becoming big.” And a letter to the New York Times cautioned the paper not to “throw doctors under the bus … as the cause of health care costs.”

“To throw someone under the bus” is defined as meaning “to sacrifice; to treat as a scapegoat; to betray,” but I think the key to the phrase really lies in the element of utter betrayal, the sudden, brutal sacrifice of a stalwart and loyal teammate for a temporary and often minor advantage. There is no retirement dinner, no gold watch, for poor schmuck “thrown under the bus.” On the contrary, the scapegoat’s name is liable to disappear from the website overnight.

The earliest solid example of “throw under the bus” found in print so far is from 1991, although a 1984 quote from rock star Cyndi Lauper where she uses the phrase “under the bus” (without “throw”) may or may not count as a sighting. Incidentally, by far the best compilation of citations for the phrase can be found, as usual, at Grant Barrett’s Double-Tongued Dictionary website (www.doubletongued.org).

The exact origin of “thrown under the bus” is, unfortunately, a mystery. Slang expert Paul Dickson, quoted by William Safire in his New York Times magazine column, traces it to sports, specifically the standard announcement by managers trying to get the players to board the team bus: “Bus leaving. Be on it or under it.” The phrase does seem to be popular in sports circles, but few of the citations I have seen from sports publications carry the same overtones of casual, callous betrayal that one finds in non-sporting uses.

Consequently, I have my own theory. I don’t think the “bus” was ever the team bus. As someone who spent a lot of time standing on Manhattan street corners and narrowly avoided being expunged by speeding city buses on several occasions, to me the phrase conjures up the classic urban nightmare of being pushed in front of a bus. As a way to quickly and irreversibly get rid of someone, “throwing” them under a bus in this sense would be the ideal solution and would satisfy the connotations of sudden, cold brutality the phrase usually carries. So I suspect that the phrase has urban origins, and migrated into sports world via players from big cities.