I have repeatedly heard the claim that the first initialism in the modern sense (meaning an acronym that is pronounced and used as a word in its own right) is ANZAC, the Australian and New Zealand Army Corps which suffered severe losses at Gallipoli during WWI.
It was in actual use during the Roman Republic, and the Empire, with its desire to maintain the illusion that the republican constitution was still in force, kept using it for a while. It is, in fact, a very succinct formula that summarises neatly the character of governance in Rome at the time as combining a democratic and an oligarchic element. Well into the modern era, self-governing European city states would adopt and adapt the phrase, replacing the final R with a letter abbreviating the name of the city in question.
I think the various Rabbi names disprove that, even if they’re only medieval and not ancient.
Acronyms do require the use of an alphabetic writing system and the Babylonians didn’t have one of those. So that’s why they didn’t use them. Maybe the Phoenicians had them.
As far as English language acronyms, as noted above, they first started to flourish in the 1930s with all the New Deal organizations. However, there is a prehistory, so to speak.
First, there’s one acronym that goes back to WWI: AWOL. There are stories putting its origin back to the Civil War, but those are not considered creditable.
Second, during the late 19th century, there were a few towns named from initialisms. That is, when the founders were stumped to come up with a name for a new town, someone suggests they take the initials of the town founders or some other group and arrange them into a pronouncable name. The earliest of these I could find is Le Mars IA, which was named in 1870. The following year, Delmar IA was also named that way, and in 1872, Primghar IA joined the parade. There’ve been a number others which I compiled into this list
Finally, also during the late 19th century, large corporations arose and they were sometimes refered to by their acronym. I haven’t looked into which one was the earliest, but I would guess one of the railroads. But it wouldn’t surprise me if there were a few from the early or middle 19th century.
Should have double-checked with M-W online. Turns out my info was out-of-date on when AWOL was first used. The earliest known use is now thought to be 1891. Which easily pre-dates ANZAC, by the way.
Even 1891 is rather late for a beginning. A word column in the New York Times:
In English, the first known acronyms (as opposed to plain old initialisms) cropped up in the telegraphic code developed by Walter P. Phillips for the United Press Association in 1879. The code abbreviated “Supreme Court of the United States” as SCOTUS and “President of the…” as POT, giving way to POTUS by 1895.
I can’t find any newspaper hits before 1890 for SCOTUS and it was still being explained in 1895. The Times itself did not use the acronym that early. However, The Buffalo Times for 26 Nov 1890, p. 2, definitely used the term without explanation, in a syndicated article datelined Chicago.
Interesting. I had no idea SCOTUS was used that early. Or POTUS.
Still not earlier than CABAL 
The Great Western Railway was known as GWR pretty much from its start in the 1830’s.
I presume you are referring to
I’ve heard that the National Biscuit Company was the first, though then you have to define whether it counts as an acronym, since they used the first two letters of each word.
My first thought!
1520s, “mystical interpretation of the Old Testament,” later “an intriguing society, a small group meeting privately” (1660s), from French cabal, which had both senses, from Medieval Latin cabbala (see cabbala). Popularized in English 1673 as an acronym for five intriguing ministers of Charles II (Clifford, Arlington, Buckingham, Ashley, and Lauderdale), which gave the word its sinister connotations.
All upper class Brits of the day would know enough French to know about cabal’s meaning of intrigue and secrecy. Some scurrilous pamphlet writer seized the coincidence with the five conspirators and made their initials, which fit the word, famous in the long term.
In the short term, that cabal wasn’t much. They weren’t conspirators but the King’s Privy Council. The word cabal evidently was used about earlier council members. Maybe we should think of them as the precursors to the Deep State.
And scholars tend to belive the first gospel was written by Q.
The author of the first gospel didn’t call himself “Q”, though. That’s a label used by modern scholars to refer to a hypothetical document that’s never actually been found. If it were found, we might know what the author actually called himself.
We call ourselves “Q”, or thou mayest call me that. 'Tis all much the same.
Yes, but note the smilie. It was just a joke, since the origin of cabal actually goes back to Hebrew and is not an acronym.
Q is an abbreviation of the German word Quelle, meaning source.
Ah. Humour is not lost on some…
The text is biblical, but the abbreviation is a medieval tradition. The gospels tell us the text of the sign but not that it was abbreviation. In fact, John tells us the sign was trilingual (Hebrew, Greek, Latin), which would imply it was not abbreviated.
Yes, definitely not 2000 years old. I don’t know when the Latin text was first used. Attributed to John 19 where the three languages were mentioned, but it was written in Greek originally as far as I know (which is not very far).