It just means that it is a representation of some other wealth. Gold isn’t fiat because gold itself is the thing that has value, currency is fiat because it is a representation of value not in and of itself valuable.
All currency is by definition fiat because all currency is a representation of value. And the crypto Bros keep telling us that bitcoin and similar are currency so they are therefore fiat.
In the song that’s what they send every single day two French hens every single day are sent so yeah at the end they do send a lot of French hens.