The formation of the word 等级 is a conceptual blend of two characters, each contributing a core idea of ordered classification. The first character, 等, originally depicted bamboo slips used for administrative records, evoking the idea of measured grades or ranks. The second, 级, pictographically represents steps on a staircase, directly symbolizing sequential levels or tiers. By combining them, the word visually and notionally constructs the idea of a structured hierarchy, where items or people are arranged in distinct, step-like grades, much like ordered records placed on ascending steps.