The origin of the word "cloud" dates back to the Old English word "clud," which means "rock" or "stone." People in old England thought clouds were large rock masses up in the sky causing storms like thunder and rain. However, the resemblance of clouds to rocks might be the connection in the choice of the word.

Over time, its meaning shifted to refer to the masses of water vapor, ice, and other particles suspended in the Earth's atmosphere. The term "cloud" is often used more specifically to refer to a visible mass of tiny droplets of water or crystals of ice that appear in the sky.