下り
くだり · kudari · JLPT N3 · noun
down-train (going away from Tokyo)
🚆 下 = down + り: from 下る kudaru, to go down; trains leaving the capital go down
Since the Edo era, travel toward the capital counted as going up (上り nobori) and travel away from it as going down. 下り is the noun form of 下る kudaru, to descend. A 下り train is the one heading out of Tokyo.
下 — horizontal line 一 + mark below
下 is an indicative character: a long horizontal line represents a reference level, and a shorter stroke placed beneath it points to the area below. The original meaning 'below, down' comes directly from this spatial diagram, and it later extended to verbs like 'descend' and 'lower'.