Currencies are used to facilitate settlement of international trade. Trade in various goods and services.

Central banks often carry reserves of various currencies to help with those international settlements and to manipulate currency values.

I see now -- the specific label of petro is wrong, but the general idea that the hegemonic control of critical commodities -> currency control is not then? And saying petrodollar would be like saying porkyuen or semiconductoryuen or something similar

That label was descriptive for a time. The times have changed, and now it's might makes right.