Sorry but gold, like every other currency, only has value because people are willing to take it in trade. Things of true intrinsic value would be useful when lost: food, shelter, tools. IE stuff we used to barter. Money exists to be an exchange layer on barter, so you don’t have to carry your chickens all over town. Anything useful, intrinsically valuable, innately makes bad money because you wind up using it for other stuff. Gold is the original fiat currency. But it was currency so long a lot of people have forgotten that it’s value is totally added by people.
Gold has been globally recognized as a currency forever, so it does not fall under the definition of fiat. Fiat is produced by a government and does not have to be backed up by anything of value.
You are correct about the bartering and the reason for currency though. Food has a value but not a lasting value as it is consumed, the real value is the means to either produce or buy more food.