You can think of echelon as one rung of a ladder. Set several things out so that each one stands a step above, behind or to the side of the last, and you get a slanting, line — planes in the sky, rows of numbers on a page, or people in an organization. Whatever the material, the picture is the same: not one flat row, but a staircase, where every position sits at a different step.
Borrowed from French échelon, a rung of a ladder, a diminutive of échelle (ladder), which goes back to Latin scāla. The ladder is still visible in every modern use.
借自法文 échelon，意思是梯子的一橫、一階；它是 échelle（梯子）的小稱形，再往前是拉丁文 scāla。今天每一個用法裡，那把梯子都還在。
Wiktionary entry for echelon, etymology section (kaikki:3f6f69a190036ae4:970552640), supplied in the evidence packet
Two branches
一階一階錯開的排列
這一組最貼近字面：東西真的排成階梯的形狀，看得見、畫得出來。
noun · C2
A line of ships, soldiers, planes or vehicles set out so that each one is a little behind and a little to the side of the one in front, so the whole group makes a slanting line with a stepped shape. This is a technical use, and it usually appears in the phrase in echelon.
梯形隊形
組織裡的層級
把那道階梯從地面立起來，變成往上爬的位階：每一階是一個層級，也是站在那一階的人。
noun · C1
One of the levels of rank or power inside an organization, a profession or a society, and also the people who are at that level. It is almost always used in the plural, and most often about the levels near the top.
階層