Due to the importance of the Roman Empire and the offshoot Byzantine Empire, it’s often forgotten that Constantinople wasn’t chosen at random; in fact, the city already existed, and it lent its name to the empire that was subsequently centered there. Byzantium, known originally as Byzantion, was an ancient Greek city centuries before it became known as Constantinople, and the etymology of Byzantion/Byzantium is still unknown. It has been suggested that Byzantion is of Thracian origin and may be derived from the Thracian personal name Byzas, which means “he-goat.” Ancient Greek legend refers to King Byzas as the leader of the Megaran colonists and the founder of the city, but the earliest name for a city on the site is “Lygos,” which likely corresponds to an earlier Thracian settlement described by Pliny the Elder in his seminal work, Natural History: “On leaving the Dardanelles we come to the Bay of Casthenes, ...and the promontory of the Golden Horn, on which is the town of Byzantium, a free state, formerly called Lygos; it is 711 miles from Durazzo.”

Pliny went on to explain that Lygos was a Thracian settlement founded between the 13th and 11th centuries BCE. The site, however, was probably abandoned well before Megara founded Byzantion around 657 BCE across from Chalcedon on the Asiatic side of the Bosphorus. The city was briefly renamed Augusta Antonina in the early 3rd century CE by the Emperor Septimius Severus, who razed the city to the ground in 196 CE for supporting a rival contender in the civil war and had it rebuilt in honor of his son and successor, Marcus Aurelius Antoninus, known as Caracalla. This new name appears to have been quickly forgotten and abandoned, with the city reverting to Byzantium after the assassination of Caracalla in 217 CE, and that’s how it would be known when Constantine fatefully moved the seat of power there over a century later.