Answer
The nickname "The Truth" was bestowed upon Paul Pierce by Shaquille O'Neal during a heated on-court exchange. O'Neal, known for his dominance and trash-talking, acknowledged Pierce's exceptional skills and proclaimed, "You can't guard me. I'm the real deal. You're just the truth." From that moment, Pierce embraced the moniker, using it as a source of motivation and a testament to his unwavering dedication to the sport.