Umm, Ken Shamrock was fighting professionally YEARS before he was ever a pro wrestler.
As previously mentioned, Shamrock started Pro-Wrestling around 1990. I believe he was trained by Buzz Sawyer and at the urging of one of the Malenko brothers got into Japan to fight.
He went by Vince Torrelli in the Carilonas, and Ken Shamrock in one All Japan match. He started Japan MMA as Wayne Shamrock to hide that he was a phony worker.