on cloud nine
The idiom “on cloud nine” means blissfully happy or joyous.
Though this saying comes from he late 19th century, nine has been a mystical number for thousands of years, back to the time of ancient Greeks. The saying originally was “on cloud seven,” probably coming from “seventh heaven,” the highest of the heavens in Jewish religious literature. Nine was then substituted, perhaps because it is a sacred Christian number. This is because three is a trinity and represents perfect unity, and nine is a trinity of trinities (3 x 3). Other idioms that express great joy also suggest being up high: “on top of the world”, “walking on air”, and so on.
Here is the idiom being used in a sentence:
Many people in Washington D.C. were on cloud nine because they received the opportunity to see the Presidential Inauguration in person.