A duck that cannot fly and can only waddle. It is still with the group, but it cannot keep up, and anyone watching can see it will not get far on its own. English hangs that picture on a person, a business, or an office-holder who is still there in name but can no longer move under their own power.
lame duck 可以想成一隻飛不起來、只能一拐一拐走路的鴨子。牠還跟著隊伍，但跟不上；旁邊的人一眼就看得出，牠自己走不遠。英文把這個畫面掛在人、公司、機構或官員身上：東西還在，位子還在，力氣沒了。所以這個詞幾乎都帶著一個沒說出口的下半句——再這樣下去，得靠別人，或者就到此為止。
From the word’s history
Wiktionary records the phrase from about 1761 in London: a trader who could not pay what he owed was said to waddle out of Exchange Alley like a lame duck. The money use came first, and what spread from it was the picture of someone who can no longer keep up.
維基詞典記載這個說法大約在 1761 年的倫敦出現：在交易所付不出錢的人，被說成像跛腳鴨一樣一拐一拐地走出交易巷。先有這個賠錢的用法，後來留下來、擴散出去的，是「跟不上、走不遠」這個畫面。
Wiktionary, "lame duck"
登入就可以看每一支怎麼連回核心畫面。