One way to hold this word: a sound that keeps coming and never turns into meaning. Think of the ba-ba-ba a small child makes — many little sounds, in a steady stream, with no word you can lift out of it. English lends that picture to three scenes. A person whose talk runs faster than their sense. A room where everyone speaks at once. Water running over stones. In each one the sound is continuous and the meaning is not there to catch, and that is the whole of the word.
From Middle English babelen, part of a Germanic family of words for chattering; the repeated ba-ba is very likely copied from the sounds small children make while learning to talk, which is why the word has always been about sound rather than sense.
來自中古英語 babelen，屬於日耳曼語族一串表示「喋喋不休」的字；裡面重複的 ba-ba 音很可能就是在模仿小孩牙牙學語。來源本身也只說「可能」，所以這是一條線索，不是定論。不過它正好解釋了為什麼這個字從頭到尾都在講聲音，不講內容。
Wiktionary 'babble' etymology, supplied in the evidence packet (source_ref kaikki:3f6f69a190036ae4:686353171:49653)
Two branches
人發出的一團聲音
這一組就是核心畫面直接用在人身上：嘴巴一直在動，聽的人撈不到字。三個意思的差別只在「誰在發聲」和「缺的是什麼」。
verb · B2
To talk fast and for a long time in a way that is hard to follow, so the listener hears a stream of words but cannot pick out the meaning. A baby who is making sounds that are not yet words also babbles.
胡亂快講；喋喋不休
水流過石頭的細碎聲
水聲這一組不是比喻人講話，而是同一個聲音條件剛好又出現一次：很多小聲音、密到分不開、沒有一個能命名。所以英文不覺得需要另一個字。
verb · C1
If a stream or other shallow water babbles, it makes a low, gentle, continuous noise as it runs over stones.
潺潺作響