The kanji for STEP/STAIR looks like a series of steps or levels. The left part (⺖, an archaic form of 'hand' or 'again') represents the repeated action of stepping, and the right part (殳, a 'weapon' or 'tool' component) suggests something solid or carved, like a finished step.
'Dan' — Imagine a person named DAN taking a STEP up the STAIRS, achieving a new RANK.
Vocabulary
階段かいだん
stairs, stairway
段階だんかい
stage, phase, step
手段しゅだん
means, way, measure
段ボールだんボール
cardboard
初段しょだん
first degree black belt (martial arts), first stage