Originally meant 'rock' or 'hill' in Old English — shifted to the atmospheric meaning around 1300, replacing 'wolcen.'
A visible mass of water droplets or ice crystals suspended in the atmosphere above the earth's surface.
From Old English 'clūd' (mass of rock, hill, a rocky eminence), from Proto-Germanic *klūtaz (lump, mass). The original meaning was 'rock' or 'hill,' not the atmospheric phenomenon. The transfer from 'mass of rock' to 'mass of vapor' occurred in Middle English around the 13th century — clouds looked like great billowing masses in the sky, just as rocks were great masses on the ground. The old word for the sky phenomenon had been 'wolcen,' which was displaced. Key roots: *klūtaz (Proto-Germanic: "lump, mass").
'Cloud' originally meant 'rock.' Old English 'clūd' referred to a mass of stone or a hill — the same root that gave us 'clod' (a lump of earth). The atmospheric meaning took over in the 1300s because billowing cumulus clouds looked like massive, lumpy formations. The original Old English word for a sky-cloud was 'wolcen,' which is now completely extinct.