The Latin cloud term introduced by Luke Howard in 1802 that means “heap” or “pile” is cumulus.
Howard, an English pharmacist and amateur meteorologist, published his cloud classification in the essay “On the Modification of Clouds.” He used Latin names so observers could describe clouds consistently across languages. Cumulus referred to detached clouds with rounded, heaped tops.
Cumulus clouds usually form when warm air rises and cools by expansion. Small fair-weather cumulus clouds are common on sunny days, although strong vertical growth can produce cumulonimbus thunderstorms. The word describes a cloud genus, not simply any cloud that looks fluffy.
Stratus means “layer,” while cirrus means “curl” or “lock of hair.” Nimbus is associated with rain-bearing clouds, but it is not one of Howard’s four original basic cloud genera.