The first recorded mention we have of the word fiat (meaning "decree") in English was in an early seventeenth century sermon, in the sentence The Lord be pleased to set His fiat unto it, and confirm it with His royal assent. At that point, it's pretty clear that it was used more in a context of approving or authorizing than ordering or commanding. The word was taken directly from the Latin third singular present active subjunctive fiat, which can best be translated as "let it be done". That traces to the Proto-Italic verb fuio ("to become") and eventually Proto-Indo-European buh, which could mean "grow" or "appear". The automobile brand Fiat has nothing to do with the noun; it's actually an acronym of the words Fabbrica Italiana Automobili Torino, or "Italian Automobile Factory of Turin".
Hello! I'm Adam Aleksic. This year, I graduated from Harvard University with a degree in Government and Linguistics. There, I co-founded the Harvard Undergraduate Linguistics Society and wrote a thesis on Serbo-Croatian language policy, magna cum laude. In addition to etymology, I also really enjoy philosophy, trivia, vexillology, geography, board games, conlanging, art history, and law.