Leonardo da Vinci's mother was a slave trafficked into Italy, an expert on the Renaissance artist has claimed.

In a new novel, a dramatized account of her life, Renaissance scholar Carlo Vecce writes that Leonardo's mother, Caterina, was originally from the Caucasus but was sold into slavery in Italy.

Entitled "The Smile of Caterina, the mother of Leonardo," the book was inspired by a discovery that Vecce -- a professor at the University of Naples and an expert on the Old Master -- made at the State Archives in Florence in 2019 when working on the 500-year anniversary celebration of the great polymath's death.

There, he stumbled across a previously unknown document he says is dated the fall fo 1452 and signed by the man known to be the master's father, which, he says, frees a slave called Caterina from her mistress, Monna Ginevra. The date, which was a few months after Leonardo was born, and fact that Leonardo's father signed it struck Vacce as proof that this woman was Leonardo's mother.

Two years earlier, according to the same document, Ginevra had hired Caterina out as a wet nurse to a Florentine knight.

"I discovered the document about a slave named Caterina five years ago and it became an obsession for me," Vecce, professor of Italian literature at the University of Naples "L'Orientale," told CNN. "I then searched and found the supporting documents. In the end, I was able to find evidence for the most probabable hypotheses. We can't say it is certain, we don't look for the absolute truth, we look for the highest degree of truth, and this is the most obvious hypothesis."

The document describes the freed slave as having been born in the Caucsus area of central Asia and trafficked to Italy.

Vecce planned to continue his research in Moscow, where he felt sure he could find even more documentation about the slave trade in Italy and Caterina's life. But the Covid-19 pandemic put a halt to his travel plans, and instead, he said, he became "obsessed" with the story.

"The more I went forward, the more the story made sense. The story of a slave who was kidnapped at 13 and liberated at 25, the year after Leonardo was born. What should have been the most beautiful years of her life were spent as a slave," he said.