First, let's look at the term psephologist. That name for someone interested in the scientific study of elections has its origin in the Greek psephos, meaning "pebble." What's the connection between pebbles and elections? Paleo-psephologists know the ancient Greeks used pebbles to cast their votes.

The ancients didn't only cast votes with pebbles, and they didn't only vote to put people into office, either. Occasionally, long-ago Athenians would vote to banish someone considered a threat to the stability of their city; when they performed this civic duty, they did so by writing the name of their candidate on broken pieces of pottery. The victim voted into this ten-year-exile was said to be ostracized after ostraca, the Greek word for "potsherd."

Now that you know the story behind ostracism, you may be able to figure out how petalism got its name. Eligible voters in Syracuse, that ancient city in southeast Sicily, used olive leaves—petalon—to vote on the fate of their citizens suspected of having dangerous influence or ambition. Such exiles were sent away for five years, not ten.