票賣到一張不剩
這是核心畫面最直接、也最無害的一面：該賣的東西賣完了，所以它是好消息。
noun · B2
A concert, play, sports game, or similar event for which every single ticket has been sold. Before a noun it describes the same thing, as in a sell-out crowd or a sell-out tour.
全部售罄的演出
核心畫面
Picture a counter at the end of a busy day with nothing left on it. Everything went out, and whoever arrives now is too late. That plain picture of selling until nothing remains is where the noun starts, and it is good news: a show with no tickets left is a success. The same picture turns hard when what went across the counter was never supposed to be for sale. A promise, a loyalty, a set of beliefs can also be handed over for money, and English uses the same word for that, either for the act or for the person who did it.
可以想成：忙了一整天之後的櫃檯，上面什麼都不剩。東西全部賣出去了，這時候才來的人只能撲空。這個「賣到一點不剩」的畫面…更多收起
可以想成：忙了一整天之後的櫃檯，上面什麼都不剩。東西全部賣出去了，這時候才來的人只能撲空。這個「賣到一點不剩」的畫面就是這個名詞的起點，而且它本來是好消息——一場票全部賣光的演出，代表很成功。有趣的是同一個畫面換個東西擺上去，味道就整個變了。如果放上櫃檯的是一句承諾、一份義氣、一套原則呢？那些本來就不該拿來賣。英文用的還是同一個字：可以指那件事，也可以指做那件事的人。所以看到 sell-out，先問一句：賣掉的是票，還是信任。From the word’s history
The noun is recorded as a deverbal form of the phrasal verb sell out — sell plus out, that is, to sell until nothing is left.
來源資料註明這個名詞是從動詞片語 sell out 直接變成名詞的：sell（賣）加 out（出去、光了），也就是「賣到一點都不剩」。這條線索正好對上兩邊的用法——票賣光是字面的，把信任賣掉是同一個動作換了對象。
Wiktionary entry for sell-out, etymology: Deverbal from sell out (evidence packet, source_ref kaikki:3f6f69a190036ae4:1225052728)
Two branches
把不該賣的也賣了
同一個「賣光」的動作，換成不該擺上櫃檯的東西：承諾、義氣、原則。畫面沒變，評價整個翻過來。這是一種理解方式，不是在說歷史怎麼走。
noun · B2
Someone who gives up what they said they stood for, or lets down the people who trusted them, in order to get money, fame, or an easier life. It is an informal word and a strong insult.
背棄原則的人