As far as I know, this is what happened:
"The father of modern meteorology" an English pharmacist named Luke Howard originally gave cloud types their names in 1803. He first introduced 3 cloud types; Stratus (layered), Cumulus (meaning "heaped" in Latin) and Cirrus (curled). He then added a forth slightly later; Nimbus (Latin for "cloud") for the rain bearing variety. This allowed him to classify virtually any type of passing cloud using a combination of these words, and a bit of a legend in meteorological circles.
This system was added to over the years and eventually was combined to produce the encyclopaedic "International Cloud Atlas" which runs to 2 volumes! This was fortunately condensed in 1896 and divided clouds into 10 basic types, of which the most comfortable, cushiony.....plumpest looking one was number 9; Cumulonimbus. This is where I believe the saying came from originally.
Please correct me if you know differently, as I'm always looking to expand my "useless information" quota!
