We Often Use Medicine Balls in Boot Camp, But Did You Ever Wonder Why They Call Them Medicine Balls? / by Stephen Cooper

I got this from Wikipedia...

"Medicine ball training is one of the oldest forms of strength and conditioning training – the first reference to wrestlers training with sand filled bladders appears in Persia nearly 3000 years ago. In ancient Greece the physician Hippocrates had them sewn out of animal skins and stuffed with sand. His patients threw them back and forth for injury prevention and rehabilitation."

So now you know.