Because he was born out of wedlock, Leonardo did not have a formal family surname; "da Vinci" simply indicated he was from the town of Vinci. Consequently, he often signed his journals and works simply as "Leonardo" or more assertively as "Io, Leonardo". Historical Significance of the Signature
: Contemporary biographers like Giorgio Vasari noted that first names were the primary way to refer to individuals at the time, and Leonardo's signature reflects this cultural norm. Media and Cultural References Io, Leonardo
The phrase has also been used in various modern contexts to evoke the artist's legacy: Because he was born out of wedlock, Leonardo