[Kevin Finnerty]

Wee Willie Keeler and John McGraw and other little pests like them used to float little backspin bunts that would land fair and then turn left and shoot foul, making it impossible to throw them out. So the third baseman would often play in shallow foul territory, because the ball could merely land fair and was playable. That was the genesis of the rule that all other players be stationed in fair territory (and also the rule requiring a batted ball to remain fair or reach a base to be fair).