"Fluctuation" implies 2 objects. What are you measuring fiat fluctuation against?
Fluctuation, usually, describes a value changing over time.
So you compare it against itself at a different point in time.
For doing so you try to keep all other factors as equal through time as possible.
So fluctuation implies at least one value/level/number in a space that changes over time.
The value of a kind of fiat is a relative quantity and so when we can only say whether or not it fluctuates with respect to something else. If we fix the quantity against which we measure we can happily talk about fluctuation in value. Most people would probably take some average of the goods and services they purchase regularly as their yardstick. In this respect fiat is remarkably stable but I wonder how much of this is because everyone prices in fiat.
If your personal list of goods and services comprises completely of "silver" then you'll find 2 to be pretty stable.
