Based on the mid-sixteenth-century biography of Leonardo da Vinci by Giorgio Vasari, many historians believe the painting is a portrait of Madam Lisa Giocondo, wife of a wealthy Florentine. It is from Vasari that the painting received the name Mona Lisa, also known as La Gioconda in Italian or La Joconde in French. But Vasari published his book thirty-one years after Leonardo's death, and he was known to fill in fact with fragments of fantasy.

Source: PBS