It appears that the ultimate source of the Veronica legend is the facial image that is found on the Shroud of Turin.
In about A.D. 30 king Abgar V of Edessa heard of a healer and teacher in Israel. He sent a messenger to find this healer and to invite him to Edessa to live there under his protection.
The messenger found Jesus who declined the invitation to Edessa, but promised to send a disciple to heal the king. Later, the disciple Thomas commissioned Thaddeus (one of the seventy) to go to Edessa and there the king summoned him.
When entering the king’s presence, Thaddeus held up a cloth which bore Jesus’ facial image. Upon seeing this, the king was immediately healed of his disease. Edessa became the first Christian city.
After the death of Abgar V, the sacred cloth was hidden and sealed in the west gate of Edessa where it remained until the early 6th century then becoming known as the Image of Edessa “made without hands” (meaning that it was miraculous in its formation.) Shroud researchers theorize that in ancient times a bloody burial cloth was regarded as an abhorrent, unclean thing and that, because of this, only the facial portion of the image bearing cloth was ever exhibited.
In 944 Emperor Romanos Lecapenos extracted the Image of Edessa though the payment of a large sum of silver and the threat of force.
The Sacred Cloth formally entered Constantinople on August 16th, 944 where it became known as the Holy Mandylion.
Iconography is a Byzantine tradition and, of course, many icons of the Mandylion were made and continue to be made to this day. A true or “vera” icon would be one that was made from direct observation of the Mandylion and then touched to the sacred cloth. Some of these true icons or “vera iconica” made their way to the Roman Church and to the Vatican itself. Yes, there were more than one, and at some point the Vatican had to intervene to settle the question as to which one was the true “Veronica.”*
How the Sacred Image of our Lord came to be imprinted on the cloth was not understood in ancient times. The linen was never fully exhibited, only the facial portion was shown.
If anyone knew that that it was in fact a burial cloth, they kept quiet about that fact. Thus many myths were invented to explain it. One was that Abgar V’s messenger was attempting to draw a portrait of Jesus when Jesus stopped him and held up the canvas to His face leaving a likeness. Another was that Jesus held a cloth to His face when praying so intensely in the garden. But these ideas fail to explain the blood and the facial bruising.
The Veronica story does better of course. Its flaw is that the ever present religious authorities would have immediately and forcefully confiscated any such image bearing cloth as both contrary to Jewish Law and inimical to their interests.
However, the Veronica theory was such an improvement over earlier postulations that you will find on some Eastern Church Mandylion icons a small representation of Station Six along with the representations of Thaddeus meeting Abgar V and the west gate of Edessa. I other words the Legend of Veronica, formed in the West, made its way back to the East!
*“HOLY FACES, SECRET PLACES,” Wilson, 1991