Uh, it was a bunch of some of us old-timers who failed to categorise bands a la Sentenced and HIM with a specific Finnish vibe. Who exactly, I don't remember. Ivan latched on to it and made it a genre I assume.
Haha, as a latecomer, I have always been interested in the "suomi metal" category on this site, which seems to be a style type that is not seen outside this place. So I am curious who first named it this way.