Think of the moment someone stops moving around and lowers themselves onto a chair. Standing means you are still on your way somewhere and can leave at any second; sitting means you have put yourself in one place and you are staying there for a while. Every meaning of sit-down comes from something that change makes possible — resting, eating properly, talking properly, or refusing to move.
「sit-down」可以想成一個很小的動作被放大來看：一個人停止走動，把身體放到椅子上。站著的時候，你其實還在路上，隨時可以走；一坐下來，你就把自己放在同一個地方，而且打算待一會兒。這個字的每一個意思，都是從「坐下之後才做得到的事」長出來的——歇一口氣、好好吃一頓、好好談一次，或者坐著不走。
From the word’s history
The source records this word as deverbal from the phrasal verb sit down: the action was turned into a thing and into a describing word.
來源把這個字記為從動詞片語 sit down 直接轉過來的（deverbal）：先有「坐下」這個動作，再把它當成一件事物、一種樣子來用，所以 a sit-down 和 a sit-down meal 的核心都還是那個動作本身。
Wiktionary (kaikki extract) sit-down: etymology_text 'Deverbal from sit down.'
登入就可以看每一支怎麼連回核心畫面。