“It is a cinch that the captain and manager of the team in the field would have put up a long and loud protest that the hit was good for only two bases, even though deep down in their hearts they knew that the ball would have gone over had it not been for the fan’s interference.” Billy Evans, “Billy Evans’ Baseball Problems (Answer to Yesterday’s Problem),” Altoona (PA) Tribune, February 18, 1914, p10
NOTE: Umpire Billy Evans used this phrase in a column he wrote that posed “you-make-the-call” type of situations and then answered them in the next column. These lines were in his answer to a question posed in the previous day’s paper. It involved a hypothetical situation in actual, if unusual, circumstances during Game 2 of the 1911 World Series between the Giants and the Athletics at Shibe Park in Philadelphia.
In order to allow more fans in to see the game, a temporary three-foot high wooden fence was installed thirty feet in front of the regular (and much higher) right field wall. Standing fans packed this new space. “It was agreed,” wrote Evans in his February 17th column, “that a hit into this section was to be good for two bases.” Some of the fans climbed up to sit on top of the higher wall for a better view. (There were no seats behind the permanent wall.)
One of the umpires, wrote Evans on the 17th, asked: “‘Suppose a batter hits a ball that would ordinarily clear the [higher] fence; suppose, as it is about to pass over the fence, one of the fans sitting on the top of the wall arises and tries to stop the progress of the ball; suppose the ball does strike his hands, but is not held and drops into the section of the field agreed on as good for two bases, how many bases should be allowed the batter?'”
Fortunately, reported Evans in the next days column, the umpires were ready with an answer. “It was agreed before the start of the game that if a fan seated on the wall attempted to make the catch, failed in his effort and the ball dropped among the fans inside the ground, the hit would be regarded as good for a home run.” That was followed by the quote above, with the earliest know use of “fan’s interference.”
In the end, the situation never arose although, as Evans reported, on Frank Baker’s 6th inning two run home run over the right field wall “one of the fans sitting on top of the wall made a desperate but unsuccessful effort to grab the ball as it sailed out of the grounds.”
A section of right field, including the temporary fence and the permanent wall with fans sitting on it can be seen in this image from the Hall of Fame, part of a panoramic view. (Follow the link to zoom in and out and pan across the entire field.)
No earliest use given in 2009 Dickson Baseball Dictionary