The "flame" description came into vogue due to a finishing process created about 100 years ago. I think Gibson may have been the pioneers, but don't quote me. Still, it wouldn't surprise me - there was no such thing as "Korina" wood until they started using the term. Everybody else in the world calls it what it is - Limba.
Marketing weenies - you gotta hate 'em.
Anyway, if you put what's now called a yellow/red or cherry burst on a piece of Curly Maple, it sorta looks like a flame effect rendered in wood. That's where the name came from. Now, everybody in the music industry calls Curly Maple "Flamed" regardless of the finish color.