Cloud Nine
According to Bill Bryson's 'A Short History of Nearly Everything', the 1896 edition of the International Cloud Atlas had ten basic types of clouds and cumulonimbus, the fluffiest was number nine, which is where the expression 'on cloud nine', meaning 'extremely happy' comes from.
The OED also lists 'on cloud seven' as an alternative form, but one that I have never heard.
Categories: General
Agree. Glad you said that.
Maybe it was in an earlier edition and got supplanted by number nine.
The etymolgy is actually unknown. As cute as this story is (most false etymologies are:)), there is no evidence at all to back it up. In fact, "cloud seven" seems to predate "cloud nine". Why would this be if it was based on the Cloud Atlas?