I learned from an article in The Sun magazine that the word eccentric comes from a Greek word that describes objects in space that don't revolve around the earth. The Greeks in ancient times saw Venus, Mercury, Mars, Jupiter, and Saturn and observed that they wandered through the sky moving in a seemingly aimless way. They called these planets asteres planetai (wandering stars). The planets were not, however, wandering. They were revolving around the sun. It was the finite view of human beings that made them seem like wanderers.
Human eccentrics move in a seemingly aimless way, too. Their movements make them seem like wanderers to other human beings with finite views. They don't wander aimlessly, though. They revolve around a different center.