The phrase "fire in the head" is a Celtic
metaphor for divine
inspiration. It ultimately derives from the "
Song of Amergin," but has cognates in the poetry of
Taliesin, whose very name means "Shining Brow."
It also appears in W.B. Yeats' poem "The Song of Wandering Aengus":
I went out to the hazel wood,
Because a fire was in my head.