"Whoever has ears, let them hear what the Spirit says to the churches. To the one who is victorious, I will give some of the hidden manna. I will also give that person a white stone with a new name written on it, known only to the one who receives it." (Revelation 2.17)
One of the commonest of all customs in the ancient Roman world was to carry as a talisman or "good luck charm" a "white stone" called a "Tessera." These could be an amulet, a charm in remembrance of someone special or as even as an entry token to the games or a banquet. In ancient Rome and Greece, a Tessera might also be made of wood or bone. A Tessera also might be made of a precious metal or a valuable semi-precious stone but often it was nothing more than a pebble, or a small piece of wood or bone chip inscribed with the initials of the giver. The word tessera also described the small glass squares put together in a wall mosaic like a painting, which would not darken from the soot of candles and could be easily cleaned to restore its original colors.
On the pebble tessera there was often a sacred name carved or written. To know a god's name was believed in ancient times to give the bearer certain powers over that god. The name of a god came with the ability to summon that god to one's aid in time of difficulty and to have mastery over demons. Such a Tessera stone was thought to be doubly effective, if no one other than the owner knew the name that was inscribed upon it. Here in Revelation, Jesus gives his faithful followers a white stone with a new name upon it, not as a good luck charm but bearing the secret and special name for Jesus.