This design is also called a staurogram or monogrammatic cross. It dates back to an early manuscript from the second century when the Greek letters T & P were superimposed over each other and used in the early Greek New Testament...

This design is also called a "staurogram" or "monogrammatic cross." It dates back to an early manuscript from the second century when the Greek letters T & P were superimposed over each other and used in the early Greek New Testament...