One way to hold this word: something that was up and moving has settled and sat down. Picture a room where everyone is seated and talking softly, or dust that has stopped swirling and come to rest on a table. Nothing is rushing, nothing is loud, nothing is bright. From that picture you get a person whose manner stays even, a town where the shops close at six, a walk that never speeds up, and the drug a doctor gives someone so that the fear or the pain settles too.
From the word’s history
Latin sēdātus (calm, composed) comes from the verb sēdō (to calm, to settle, to stop), and behind that lies the very old root meaning to sit. The verb sedate comes from the same Latin verb. So the settling-down picture is sitting inside the word's history, not only in the modern meanings.
拉丁文 sēdātus（平靜的、沉著的）來自動詞 sēdō（使安定、平息、停下來），再往上是一個很老的字根，意思是「坐」。動詞 sedate 也是從同一個拉丁動詞來的。所以「讓它定下來」這個畫面，本來就在這個字的來歷裡，不只是現代用法的比喻。
Wiktionary entry for sedate, source_ref kaikki:3f6f69a190036ae4:924793199 (adjective) and kaikki:3f6f69a190036ae4:924820671 (verb): Late Middle English sedate, from Latin sēdātus, participial adjective of sēdō, ultimately from Proto-Indo-European *sed- (to sit); the verb partly from the participi...
登入就可以看每一支怎麼連回核心畫面。