In the early 90s, you'd hear it at all of the SWC parks. Not just Olsen. We started on ball 5, everyone else started on ball 4. It wasn't an en masse thing. It would be groups of 10 or 12 or whatever doing it.
In 1997 I went to the Big 12 tournament and realized that OU and OSU did it too. This leads me to believe that Texas/OU/OSU fans were stealing material from each other in Omaha back in the day.
I've read posts that it existed at Olsen as early as the early 80s. I don't doubt that's true, but I don't think that gives us a claim to inventing it. Seems pretty far-fetched to me that pre-1989, Olsen was feeding crowd material to the teams competing in Omaha most years. I find it much more likely that we were getting it from the sips. Anyway, that's my opinion.
It started as an "everyone is doing it" thing in the late 90s. It was MUCH SLOWER then.
This story has been rehashed in probably a half dozen threads this season.