@Nep "The handshake has existed in some form or another for thousands of years, but its origins are somewhat murky. One popular theory is that the gesture began as a way of conveying peaceful intentions. By extending their empty right hands, strangers could show that they were not holding weapons and bore no ill will toward one another. Some even suggest that the up-and-down motion of the handshake was supposed to dislodge any knives or daggers that might be hidden up a sleeve."
Source: https://www.history.com/news/what-is-the-origin-of-the-handshake
Whether the source is correct or not, I don't know.