核心畫面
Think of a frame whose legs spread at the bottom, with a bar across the top, standing there empty. That shape is the whole word. The legs spread, so weight presses down and and nothing tips; the middle is open air, so the frame is light, cheap in material, and can be carried, folded or built out of a few beams. Whatever you lay across the top — a board, a table top, a railway track — the trestle is the frame underneath, never the thing it holds.
trestle 可以想成一副向外張開的腳架：兩隻腳往外撐開，上面橫著一根梁，就這樣空空地站著。重量壓下來的時候，張開…更多收起
trestle 可以想成一副向外張開的腳架：兩隻腳往外撐開，上面橫著一根梁，就這樣空空地站著。重量壓下來的時候，張開的腳往外抵住地面，所以不容易倒。中間是空的，用不了多少材料，做得輕、搬得動，也收得起來。上面要放什麼都行——一塊板子、一張桌面、一條鐵軌。重點是：trestle 指的一直是下面那副架子，不是它撐著的那個東西。From the word’s history
Middle English trestel, from Old French trestel meaning crossbeam, from Latin trānstellum, a small trānstrum (crossbeam). The oldest idea in the word may be the beam lying across the top, with the spreading legs coming to be counted as part of it later.
中古英文 trestel 來自古法文 trestel（橫梁），再往上是拉丁文 trānstellum，也就是 trānstrum（橫梁）的小稱。所以這個字最早指的可能就是橫在上面的那根木頭，後來才把下面張開的腳一起算進來。
Wiktionary entry for trestle (packet evidence): From Middle English trestel, from Old French trestel (crossbeam), from Latin trānstellum, diminutive of trānstrum.