Just like some of the way we know what the Romans wore for military outfits, the arch of Titus and other carvings, sculptures ect. Also from other historians like Josephus or some Greek historians.
I know (have read) that in some cases, we have no idea what the contemporary peoples called the coins/denominations. Examples include, if I remember correctly, what we today call the aurelianianus (antoninianus). Seems like the authoritative source could have had the forethought to come up with something less cumbersome. But, the real question is why on Earth the community came to use them as a standard. (I vote for "Anton", who's with me!)
Seems I remember names were "assigned" by collectors... Perhaps some more knowledgeable people will chime in @Bing
I am with you. It took me a while to get that one right. antoninianus. How about Antodenarius. Anything is better than antoninianus
If collectors came up with the names, then they should have been more politically correct and used "Butt" instead of "As"! I'm pretty sure that most of the names used today are contemporarily accurate, for instance, As, Denarius, Aureus, etc. But there are some where we definitely don't know the name, like roman coins that we simply call AE#. I'm sure the people back then called them something else. There's the antoninianus that I mentioned previously, but then there is also the Follis/Nummus. Nummus is Latin for "coin" but that's not what is was called back then, we don't know the word that they used for these coins.
Many(perhaps all) of the Roman Republic denominations are attested to in ancient histories such as those of Livy
Many Greek denominations are written in ancient accounts as well. With bronze that isn’t the case, though we do have a a couple.
Not me. I have no further knowledge about this topic than what has already been imparted. But thanks for the plug @Kentucky
Denarius comes from the word deni; which translates as "containing ten" meaning it was equal to 10 asses, demonstrated by the many Roman Republican coins with an X behind the obverse bust.
An edict of Constans promulgated in 356 and preserved in the Codex Theodosianus mentions two coins, the centenionalis nummus ("coin of 100 parts") and the pecunia maiorina ("large money"). Unfortunately we can't be certain as to which specific coins these names refer. The best guess is that the centenionalis is Constantine's reformed "follis" of 318-348. The name implies a nominal value of 100 sestertii. The maiorina is believed to be the billon AE2 of the FEL TEMP REPARATIO reform, issued c. 348. The nominal value of the maiorina is unknown.
The word antoninianus is formed from the root of Caracalla's actual name "Antoninus" (antonin-) combined with the Latin suffix -ianus which gives the meaning "belonging to" or "associated with". It's perfectly good Latin and, for what it's worth, falls off the tongue more easily than aurelianianus, the similarly-constructed name of Aurelian's reformed version.
Very likely the street name of money in the marketplace was something altogether different from book keeping records. Think of all the terms we use in the marketplace that we rarely write down. At the hardware store it's five bucks. In your checkbook it's five dollars. I don't know if Brits use the term quid anymore but not too long ago they did but I'll bet they didn't use that term at the bank. I can't imagine Marcus at the market stall charging "tres pecuniae maiorinae" for anything. What I'd like to know are the nicknames of Ancient coinage like Owls for Athenian tetradrachmae or Corinthian Colts for their staters. Unfortunately, these street terms, except in comedic plays, did not make into written accounts. I wonder what they called the one on the left of these two?