Thumbs(?) Up(?): You may have heard that the "thumbs up" sign shown to gladiators was the signal to spare a fallen foe and that the thumbs down was the signal to slay him. Or you may have heard the revisionist version that reversed the signs -- up for slay, down for spare. Well, I'm here to tell you that real historians and archeologists -- as opposed to purveyors of legends -- don't know up from down. There is no indication anywhere in written records, in pictures or other graphic representations, or in artifactual evidence that up or down meant anything. The only references to thumbs in the arena, found after years of diligent digging by obsessive researchers, are a few that mention the crowd or the emperor "showing the thumb" to indicate that the loser was really a total loser. And in none of the references found thus far is there any mention of the thumb being up or down.

"The finger", so often raised in anger and occasionally in a long distance proposition, is, as they say, a whole nother story. Contrary to legends about the English inventing "the one finger salute" at the Battle of Agincourt in 1415, the gesture was already well known in ancient Rome, where it was known as the digitus infamis or digitus impudicus (the infamous or indecent finger).  Literary references are quite clear (and blunt) about the meaning of the gesture. Caligula was said to be particularly fond of it, but we know what kind of guy he was. As with the thumb gesture, however, there is no extant drawing or description of exactly how "the finger" was deployed.

Internet links:

The thumb: http://www.ur.ku.edu/News/97N/SepNews/Sept29/thumbs.html

The finger: http://www.ur.ku.edu/News/97N/SepNews/Sept29/thumbs.html, which also includes a retelling of the Agincourt legend.

Bonus: an amusing and completely inaccurate theory of the origin of the most common four-letter English language vulgarity: http://historymedren.about.com/homework/historymedren/library/bletym.htm

Other interesting "straight dope": http://www.straightdope.com/index.html.