The insult in byzantine was aimed at an empire that called itself Roman

A Greek town on the Bosporus

The word points first at a place, not a person. Byzantium was a Greek colony on the European side of the Bosporus, settled by Megarians under a leader named Byzas around 657 BCE, though Byzas belongs to legend and the year to tradition.² The settlement soon outgrew that founding story. Constantine dedicated the refounded city as New Rome in 330 CE, and it became Constantinople.² The empire that ruled from it called its people Romaioi, Romans, and would hardly have thought "Byzantine" a word for itself.³

An empire named at a scholar's desk

The name it never used arrived late, and from a library. In 1557 the German scholar Hieronymus Wolf published Corpus Historiae Byzantinae, a collection of the eastern empire's sources, and became the first to file that empire under "Byzantine."⁴ The label spread slowly. It was not standardized until the eighteenth century, when French writers, Montesquieu among them, made it ordinary.⁴ The place-adjective was a cataloguer's convenience, fixed to a state that had answered to a different name for its whole life.

Gibbon's tedious and uniform tale

The fall from proper noun to insult was the work of Enlightenment historians who found the eastern empire contemptible. Montesquieu, in 1734, had already cast its long decline as a failure of attention: as the Turks closed on the capital, its people "were more preoccupied with the Council of Florence than with the Turkish army."⁵ Edward Gibbon then gave a volume of his Decline and Fall over to the empire with open reluctance, and opened the account with a verdict.

Out of that reputation for decadent, impenetrable rule, English took a lowercase adjective. The word had been in the language since 1651 in its plain sense, of Byzantium and its empire;¹ the figurative sense, intricate and complicated, is not attested until 1937.⁷⁸ The charge was never a fair account of the state Constantinople actually ran. The very name, Britannica notes, "illustrates the misconceptions to which the empire's history has often been subject."³ It stuck anyway.

What a byzantine debate is now

Four centuries on, the word does exact work. In 2015, Bloomberg described Louisiana legislators and Governor Bobby Jindal as "engaged in a byzantine debate about what constitutes a tax increase" as they tried to close a $1.6 billion budget gap.⁸ It is tangled in a way that looks built to obscure. Computer science borrowed the same reputation in 1982, when Leslie Lamport, Robert Shostak, and Marshall Pease named the problem of reaching agreement among generals of the Byzantine army while traitors send conflicting messages "The Byzantine Generals Problem."⁹

That is the distinction the word keeps, and why it holds its place. Byzantine does not just mean complicated. It marks complexity that looks deliberate, a tangle no one will admit to having built. The Enlightenment aimed the charge at an empire that never answered to the name, and it has stayed useful because that kind of complexity never went out of production.