云 began as a simple curling swirl — the shape mist or smoke makes as it drifts and turns. That same little swirl was soon borrowed to write a completely different, very common word: "to say" (moving air carries a voice too). To keep sky and speech apart, scribes stacked the rain-cloud radical 雨 on top, giving clouds their own character, 雲. When Chinese simplified its script in the 20th century, that rain-roof was lifted back off, and 云 returned to its original, ancient swirl.
A piece of culture
Auspicious clouds Cloud patterns (云纹) are one of the oldest decorative motifs in Chinese art, curling across Shang bronze vessels, Han roof tiles and imperial silk robes for three thousand years — always a spiral, echoing the very shape 云 began as. "Auspicious clouds" (祥云) were said to gather over worthy rulers and holy places; the 2008 Beijing Olympic torch was named 祥云 and carried that same ancient curling pattern into the modern flame. In classical poetry clouds became a symbol of impermanence too — Du Fu compared drifting clouds to how quickly life itself can change shape.
Use it in a real word
白云
báiyún · baak6 wan4
white cloud(s) — a favorite image in Chinese poetry; you already know 白