Thanks for asking.
There are several legends behind the origin of Sex at Noon
Feel free to choose the one you prefer, or suggest a new one:
Sex At Noon, Taxes is a funny palindrome sentence (you can read it from left to right and both right to left). Thought it might make a great website name.
Noon is the best time to have sex. Thought it might be worth to share the news.
Here there are 284 anagrams of Sex At Noon. The real meaning might be hidden there.