frn?

[SadieKate]

Ah. My guess would be he's one of those fringe tax-resister types, and FRN stands for Federal Reserve Note, i.e. paper money.

Is it just this one guy who's using the abbreviation? Or are you seeing it in different places?

Multiple people are using it on one specific forum though I think I've seen it other places, but they could be posting using a different name. It's definitely being used by the folks ranting about costs, taxes, etc. Federal Reserve Note makes absolute sense, or at least close enough that I don't have to keep doing