the 炎 in 炎遁, or En in Enton, is a kanji made up of two 火 (fire) stacked on top of each other and in everyday use would mean the act (verb) of ignition, or setting afire. I think the closest english translation in this case would be Inferno Release, or something to the effect. In asian culture/lore (and some western ones too) there are legends of indistinguishable fires like the "三昧眞火" (True Samādhi Fire) from "Journey to the West". Amaterasu was clearly based off of these kinds of mythology, and Enton probably is too.
Edit/Note: It's not that "Flame Release" is grammatically wrong in the purely dictionary sense. It's just that the feeling conveyed by "Flame Release" doesn't emphasize Enton's obvious power increase over an ordinary "Fire Release", at least IMO.
So either someone in the viz translations department read my post and thought it was a good idea, or I'm clearly a clairvoyant. Go figure.