echelon (n.)
1796, "step-like arrangement of troops," from French échelon "level, echelon," literally "rung of a ladder," from Old French eschelon, from eschiele "ladder," from Late Latin scala "stair, slope," from Latin scalae (plural) "ladder, steps," from PIE *skand- "to spring, leap" (see scan). Sense of "level, subdivision" is from World War I.