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. Yet another explanation is that the handshake was a symbol of good faith when making an oath or promise. When they clasped hands, people showed that their word was a sacred bond.

“An agreement can be expressed quickly and clearly in words,” the historian Walter Burkert once explained, “but is only made effective by a ritual gesture: open, weaponless hands stretched out toward one another, grasping each other in a mutual handshake.”

One of the earliest depictions of a handshake is found in a ninth-century B.C. relief, which shows the Assyrian King Shalmaneser III pressing the flesh with a Babylonian ruler to seal an alliance. The epic poet Homer described handshakes several times in his “Iliad” and “Odyssey,” most often in relation to pledges and displays of trust. The gesture was also a recurring motif in the fourth and fifth century B.C. Greek funerary art. Gravestones would often depict the deceased person shaking hands with a member of their family, signifying either a final farewell or the eternal bond between the living and the dead. In ancient Rome, meanwhile, the handshake was often used as a symbol of friendship and loyalty. Pairs of clasped hands even appeared on Roman coins.

While the handshake had several meanings in the ancient world, its use as an everyday greeting is a more recent phenomenon. Some historians believe it was popularized by the 17th-century Quakers, who viewed a simple handclasp as a more egalitarian alternative to bowing or tipping a hat. The greeting later became commonplace, and by the 1800s, etiquette manuals often included guidelines for the proper handshaking technique. As is often suggested today, the Victorian shake was supposed to be firm but not overly strong. One 1877 guide counseled its readers that, “A gentleman who rudely presses the hand offered him in salutation, or too violently shakes it, ought never to have an opportunity to repeat his offense.”