該習語原為美國氣象用語。該習語的流行據說應歸功于50年代播放的一個名叫《約翰尼•多拉爾》的廣播節目。Be on cloud nine的字面意思是“坐早九重云霄之上”，引申為“高興得不得了”或“飄飄然”。例如：He was on cloud nine after winning the competition. （他在比賽勝利后欣喜若狂。）

A: You seem to be on cloud nine these days. How is your restaurant business? 你近來有些高興得飄飄然。餐館的生意怎么樣？
B: How is my business? It’s none of your business! 我的生意怎么樣？這不關你的事。
A: It’s rude of you to talk to me like this. 你這樣跟我說話太粗魯了。
B: I was only teasing you. You see, we have our clients eating out of our hands now. Both Mark and I are feeling on the top of the world. 我只是在逗你玩兒。你看，我們現在已經有了許多回頭客了。馬克和我都感到非常高興。

來源:可可英語 http://www.ccdyzl.cn/kouyu/201003/99434.shtml