The picture you can hold for pontoon is a big box, closed on every side, with nothing inside it but air. Air is light, so the box will not go under; put weight on top and it pushes back up. Line a row of these boxes across a river and lay boards over them, and people walk over water. Bolt two of them under a plane instead of wheels, and the plane can come down on a lake. One picture, two places.
From the word’s history
Recorded as coming through French ponton from Latin pontō, pontōnem (a ferryboat), from pōns (a bridge). The word starts out already carrying both halves of the modern picture: something boat-like that lets you get across.
來源記載它經由法文 ponton，來自拉丁文 pontō（渡船），再往前是 pōns（橋）。這個字一開始就同時帶著「船」和「橋」兩半，正好就是它今天的畫面：用船一樣的東西，讓人過得去。
Wiktionary, "pontoon"
登入就可以看每一支怎麼連回核心畫面。