answer:What’s up with seven? Why seventh Heaven? Why seven deadly sins? Why lucky number seven? Each phrase developed on its own, and only taken together does there seem to be something mystical. But some of the phrases themselves do have explanations. “Seventh Heaven” and “cloud nine,” for instance, are probably related. The former refers to religious lore in which the seventh level of Heaven is the highest level and the dwelling place of God. The phrase “cloud seven” precedes the phrase “cloud nine” and seems to have been a reference to the notion of “seventh Heaven.” At some point, the phrase changed to “cloud nine.” Because the timing works out, popular etymology has it that this was due to a cloud atlas being published which classified various types of clouds and placed type nine as the highest cloud. This may not be correct, but it’s the best going theory we have at the time. The apotheosis of accumulated coincidences gives us mysticism.