Why "The golden money is the best one" doesn't work, I think, for this sentence:
"Golden" tells us that this "money" is physical, likely coins. However, the word "money" is uncountable in English, so linking it to a specific number doesn't sound right.
"Money" is most commonly used in English as a mass noun. We might have a "little money" or a "lot of money," but we never have "one money" or "twenty-seven monies."
I can't think of an instance right now where putting a number in front of "money" or "monies" sounds right to me. So it won't work as a subject complement following a linking verb either.
You might say: "The golden money is the best kind." But Duolingo probably would count that as incorrect because you added the word "kind."
Do you think they had cards at the time, or bank accounts?
You don't know "gold money", because you never used one. There were silver money (= all the coins made of silver), copper money, gold money. It's a category of coins.
The value (especially the modern economic meaning) is only derived from the "coins" meaning. By the way, the money is more and more immaterial nowadays, probably our great grandchildren won't even imagine that currency could be something that is material.
A current medium of exchange in the form of coins and banknotes; coins and banknotes collectively.
"I counted the money before putting it in my wallet"
Formal: sums of money.
"a statement of all moneys paid into and out of the account"
the assets, property, and resources owned by someone or something; wealth.
"the college is very short of money"
We have thought fit to order that certain pieces of gold money should be coined, which should be called “ sovereigns or twenty shilling pieces"
From: "The London Gazette, 1590".
I make no doubt, that you will understand the distinction between Paper-Money and Gold-Money
From Cobbett's Political Register, 1810.
On the 9th July of the same year, this king issued three new sorts of gold money.
From another 1808 book, etc...
For the etymology and the meaning of the word, Money comes from the French Monnaie, meaning currency, and coins.
from Latin moneta "place for coining money, mint; coined money, money, coinage," from Moneta, a title or surname of the Roman goddess Juno, near whose temple on the Capitoline Hill money was coined.
Well, I don't know if it's "semantically weird"--not exactly sure what that means actually--"gold money" just sounds weird to me in my English. Functionally, "gold money" (pecunia aurea) in my English means "gold coins". But there's another word for "coin" in Latin, nummus, so you can't use "coin" in English here because they don't use nummus here in Latin. Hmm ... Sometimes knee-jerk literal translations aren't a good idea. Now in my English "gold standard" would mean something. (I live in a very conservative area.) And maybe that would actually work here too. If, pecunia aurea est optima means, "gold money is best", and if by "gold standard," we mean that our currency (money) is based on gold, which would include the minting of gold coins and the actual ability to get actual gold (coins/bullion) in exchange for the paper currency/money that we have, well then, "The gold standard is best" should actually be a good translation. Hmm ... But I'm guessing not. What's the Latin for "gold standard"?