高原
gāo yuán · HSK 5
plateau
⛰️ 高原 = high (高) + plain/field (原) → high plain = plateau
高 means high or tall; 原 means plain, field, or source. Together they form high plain — literally an elevated flat land, which is what a plateau is.
高 — pictograph of a tall building/tower
高 is a pictograph of a tall structure, likely a watchtower or multi-story gate, with a roof on top, an upper chamber, and a base below. From this concrete image of height it extended to the general meanings 'tall,' 'high,' and figuratively 'lofty' or 'noble.'
原 — cliff 厂 + spring 泉 (white 白 + water 水)
Originally a pictograph showing a spring of water flowing out from beneath a cliff, depicting the source of a stream. From this concrete image of a water source, the meaning extended to 'origin,' 'source,' and 'original.' A separate character 源 was later created with the water radical 氵 to keep the literal 'spring' sense.