Picture a closed jar standing in a warm corner. Nobody is touching it, and yet something inside is working: bubbles climb the glass, the smell sharpens, and what comes out weeks later is not what went in. One way to hold this word is that the change comes from the inside and takes its own time. A jar of juice does it. So does a room full of people.
The packet traces ferment to Latin fermentum, the thing that makes something ferment, possibly connected to fervere, to boil, the same family as fervent. The boiling picture is why one word covers a jar and a whole society.
證據裡追到：ferment 來自拉丁文 fermentum（讓東西發酵的那個東西），可能跟 fervēre（沸騰）有關，跟 fervent（熱切的）同一家族。來源本身就帶著「沸騰」的畫面。這也說明為什麼同一個字可以從罐子一路用到整個社會。
Wiktionary (kaikki extract) via evidence packet: ferment, etymology_text (Latin fermentum, possibly from fervere; see also fervent)
Two branches
罐子裡的發酵
這一組是字面上的那個罐子：酵母或細菌在裡面工作，糖變成酒精，或者味道變酸、變濃。
verb · B2
When fruit juice, beer, wine and drinks like these ferment, the sugar in them slowly changes into alcohol. You can also ferment something, which means you let that change happen on purpose.
發酵（糖變成酒精）
社會在沸騰
把罐子換成一個國家或一個行業，冒泡的就變成人的情緒和想法。畫面一樣：從內部發生、停不下來、最後出來的東西跟原來不同。
noun · C2
A time when the people in a country or a group are very excited, angry, or full of new ideas, so that things change fast and nothing feels settled — often because of political change.
動盪；騷動；沸騰