You can picture knockdown as one short movement: something is struck, and it goes down. A boxer goes down onto the floor of the ring. A price is pushed down until it looks like a bargain. An argument puts the other side down so they cannot answer. A is taken down into flat pieces and carried away. In a lab, a gene's activity is turned down until it is quiet. The two parts of the word stay visible the whole time — knock, then down — so the useful question in a new sentence is simply: what is being sent here?
「knockdown」可以想成一個很短的動作：被敲一下，然後往下掉。拳擊手倒在地板上。價錢被壓到看起來像撿到便宜。一個論點把對方壓得答不出話。櫃子被拆成一片一片放平帶走。實驗室裡，基因的活性被調低到幾乎沒聲音。這個字的兩個部分一直看得見：knock（敲）和 down（往下）。所以遇到新句子時只要問一件事：這次被打下去的是什麼？
From the word’s history
The source gives the word as knock + down, with no older story behind it. The modern uses all keep both parts in view.
來源資料只說這個字是 knock 加 down 組成的，沒有更早的故事。今天每一個用法，兩個部分都還看得見。
Wiktionary, "knockdown"
登入就可以看每一支怎麼連回核心畫面。