Why Do We Call Galileo by His First Name Only?
The surname Galilei derives from the given name of an ancestor, Galileo Bonaiuti, a physician, university teacher and politician who lived in Florence from 1370 to 1450; his descendents had changed their family name from Bonaiuti (or Buonaiuti) to Galilei in his honor in the late 14th century. Galileo Bonaiuti was buried in the same church, the Basilica of Santa Croce in Florence, where about 200 years later his more famous descendant Galileo Galilei was also buried.
It was common for mid-sixteenth century Tuscan families to name the eldest son after the parents’ surname. Hence, Galileo Galilei was not necessarily named after his ancestor Galileo Bonaiuti. The Italian male given name “Galileo” (and thence the surname “Galilei”) derives from the Latin “Galilaeus”, meaning “of Galilee”, a biblically significant region in Northern Israel.
The biblical roots of Galileo’s name and surname were to become the subject of a famous pun. In 1614, during the Galileo affair, one of Galileo’s opponents, the Dominican priest Tommaso Caccini, delivered against Galileo a controversial and influential sermon. In it he made a point of quoting Acts 1:11, “Ye men of Galilee, why stand ye gazing up into heaven?”.
The Italian astronomer’s name is unusually confusing because both Galileo and Galilei were surnames used by his family for generations. (An equivalent might be “William Williams.”) This was not a particularly common practice at the time. Moreover, the name Galileo itself, although not completely unique, was quite rare. This is part of the reason we continue to use his first name only—it’s unambiguous.
In Renaissance Italy, individuals didn’t even stick with the same second, or identifying, name throughout their lives. Many used their family surnames one day and place of birth the next, depending on the circumstances. Take Leonardo da Vinci. Because Vinci was a very small town, calling himself Leonardo from the town of Vinci left little room for confusion—unless, of course, he was in Vinci at the time. (Leonardo was a common name.) In that case, the artist would probably have called himself Leonardo di ser Piero da Vinci, making reference to his father.
Once he became famous, he often signed his name simply “Leonardo.” Galileo referred to himself sometimes by first name only, sometimes as Galileo Galilei, and sometimes as Galileo Galilei Linceo (a nod to his alliance with a progressive group of scientists, which served, in part, as a kind of honorific). Also, because the convention was so casual, some individuals weren’t consistent with spelling or construction. Negri, Negro, de Negro, or Neri might all refer to the same person.
The governments of the various Italian city-states eventually grew frustrated by their citizens’ constantly shifting last names—without standardization, it was difficult to levy taxes or enforce military registration requirements. Beginning in Galileo’s lifetime, therefore, laws swept through Italy requiring parents to record both first and last names for their children. If a family had a traditional surname, they usually used that. If not, they resorted to town of origin or occupation, and then these names were passed down through the generations.
For the first time, a person named da Vinci might not actually be from Vinci. A man named Ferrari might not be a blacksmith. Italians also had to record their names upon marriage and death with either church or state authorities, depending on the area. Italy was a bit of a latecomer in this regard. Many nearby countries, like France and Germany, had systematized surnames generations earlier. This is probably why we don’t refer to Johannes Kepler, Galileo’s colleague and regular correspondent, or Nicolaus Copernicus, who pre-dated Galileo, as Johannes and Nicolaus.