Q: I know a capital is a city that’s the seat of government and a capitol is a building where legislators meet. But why are the two words spelled differently?
A: The words “capital” and “capitol” come to us via different etymological routes. “Capital” is derived from “capitalis,” an adjectival form of “caput,” which means head in Latin. “Capitol,” on the other hand, comes from the Capitolium (the Temple of Jupiter) on the Capitoline, the tallest of the seven hills of Rome, though it can be traced to “caput” too.
The adjective “capital,” as in a head or capital city, probably originated in the early 15th century, according to The Barnhart Concise Dictionary of Etymology. But the noun “capital” (meaning a capital city) didn’t show up in any published references until the 17th century, according to the Oxford English Dictionary.
Bryan A. Garner, in A Dictionary of Modern American Usage, writes that a governor of Virginia decided in 1698 to name the seat of the General Assembly after a temple in Rome. The idea caught on. Since then, buildings have been “capitols” and cities have been “capitals.”
Interestingly, the word that’s not a capital is the one that’s capitalized when it refers to the building where the U.S. Congress or a specific state legislature meets.