Stereo Temple Pirates would have been much more badass IMO B)
After they found out Mighty Joe Young was taken, they were toying around with different ideas. Someone (I believe Rob) remember how he/everyone used to have Stone Temple Pilots stickers (motor oil) on their bikes back in the day. He thought they would be cool initials so they starting thinking up variations on it. They've come up with many bullshit meanings for the name, like when Dean said that it was because your body is the Temple and you're the pilot of your own destiny or some cockamamy shit. In the end though it has no real meaning.