What is the source or etymology of this use of "ton"? Is it merely idiomatic?

Here in North America, "ton" is used to describe a massive hit in baseball, usually a home run traveling in the range of 500 feet.

Here's a typical example quoted in a column in the Miami Herald a couple of months ago:

"Sammy Sosa hit a home run that traveled an estimated 495 feet but surely will be upgraded beyond 500 feet, maybe even a mile or two, in the years to come. ''I thought it went out of the whole park,'' Cubs manager Dusty Baker said. ''He hit that ball a ton.'' Said Sosa: ``That was the right moment to hit that ball.''

Complete article:
http://www.miami.com/mld/miamiherald/sports/columnists/jeff_miller/6967650.htm