Picture a body as something with unwanted stuff built up inside it, and a stretch of days set aside to get that stuff out. Nothing is added during those days; things are only taken away and waited out. That stretch of time is what detox names, and every use of the word keeps that shape: a period, a clearing out, and someone waiting for it to finish. The word itself is a long medical term, detoxification, cut short — so even its shape is something trimmed down to what is left.
Detox is a clipping of detoxification, the word for removing toxins; the short form keeps the whole picture and just drops the long ending.
detox 是 detoxification（去除毒素）剪短來的形式。字根 toxin 就是毒素。剪短之後畫面完全沒變，只是把長長的字尾丟掉了。
Wiktionary etymology supplied in this packet (kaikki:3f6f69a190036ae4): 'Clipping of detoxification.'
Two branches
醫療上的戒斷：身體把物質排掉的那幾天
這一家最貼近核心畫面，而且是真的醫學。一個人停止喝酒或用藥之後，身體需要幾天把剩下的物質排出去，那幾天最難受也最需要照顧。所以 detox 在這裡同時指那段療程、那段時間，還常常指進行治療的那個地方。
noun · B2
Special medical treatment that helps someone stop drinking alcohol or taking drugs, covering the first days while the body is still clearing the substance out. The word is also used for the ward or clinic where that treatment is given.
戒斷治療
飲食與延伸：把「清空」的畫面借出去用
這一家把上面那個醫學畫面整個借走，用到沒有醫學問題的身體上，再借到身體以外的東西上。要注意字典在這裡用的是「據說可以清除有害物質」的說法，那個「據說」是這一家共同的底色：畫面很有說服力，但畫面不等於證據。
noun · B2
A period of days when someone eats no solid food, or drinks only juices, soups or special teas, in the belief that this clears harmful substances out of the body.
排毒（斷食或果汁療法）