I've had this riff in my head for quite some time. One of the inspirations, believe it or not, is the band Suicide Silence. I took note of a chord they used during chugging sections, where the bottom string is fretted but the two adjacent ones are left untouched, and thought it'd be interesting to make use of.

There's several visual connotations I experience when listening to this song, but I think fire is the best fit out of the lot, so that's how it got its name.