(1) This acronym represents the Apostle Paul's phrase, "the powers that be." It is from his letter to the Romans, chapter 13, verse 1.
(2) It was used by Joss Whedon's "Buffy the Vampire Slayer" and "Angel" TV series to describe a specific group of supernatural beings, whose purpose was to maintain the balance of good and evil in the world.
"The powers that be (TPTB) are ordained of God." Romans 13:1