The word nimbosity popped up on HH this week—an eighteenth century term for the storminess of a sky:
Nimbosity derives from the adjective nimbose, meaning “cloudy” or “stormy”, which in turn comes from the Latin word for a cloud, nimbus. And yes, that’s the same nimbus as in cumulonimbus (which combines it with a Latin word, cumulus, meaning “heap”) and nimbostratus (which literally refers to a “spreading” of cloud).
Nimbus also crops up in a handful of obscure words like nimbification (“the process of cloud formation”), nimbopallium (“a sheet of cloud”) and nimbated (“surrounded by a halo”). But it can also be used in English in its own right to describe the cloud-like aura or luminosity supposed to surround supernatural beings or deities—which is also known simply as a nimb.
Being nimble, however, is completely unrelated: