kek
The sign was originally derived from a symbol used in Roman art to indicate speaking, and first gained popularity as a Christian symbol shortly after Constantine's issue of the Edict of Milan in 313 AD, allowing Christians to practice their religion freely, without the threat of persecution. Indeed, Constantine himself converted to Christianity, and Christian art flourished. In early images of Christ, one can see an early manifestation of the sign of benediction in which the thumb is closed over the palm, rather than open. As Christian art evolved, symbols, including Christ's hand gestures, took on deeper significance. With the thumb opened, the three open digits came to represent the Trinity (The Father, Son, and Holy Spirit), while the two closed represented the dual nature of Christ as both man and God.
So it depends on who you listen to. And who has the open thumb.
You're welcome.