Thumbs-Up & Masculine Virility

Phallus worship? Phalluses in a temple in Krabi, Thailand.

I was reading Angels & Demons by Dan Brown and came across this paragraph:

"One of the free fallers, an obese woman, maneuvered toward the window. She was being buffeted by the air currents but grinned and flashed Langdon the thumbs-up sign. Langdon smiled weakly and returned the gesture, wondering if she knew it was the ancient phallic symbol for masculine virility."

I was wondering whether Brown made up that piece of information, or did he write it based on solid facts.

So I did a random search and according to WikiAnswers:

"The thumbs-up is the original sign for masculine virility. Virility, coming from the work virile means to be masculine and show signs of a grown man. In past centuries people have used the thumbs up as a sign of an ideal male specimen."

Who would know that a common finger gesture like the thumbs-up sign holds a completely different meaning altogether.

And I think the founder of Kacang Ngan Yin didn't know the original meaning of the thumbs-up sign either.