"Hikuuken" sounds like it's similar in concept to Neji/Hyuuga Clan's "Kuushou"("Vacuum/Sky/Air Palm") from Naruto. So, it should be something like "Reinforced Air Fist" or "Reinforced Vacuum/Sky Fist". Well, the "Reinforced" part comes from "rook" that the TL mentioned(as I don't know what the kanji is)...but I thought "hi" means something like "flying" in this case? Though, both "reinforced" and "flying make sense in a way. "Reinforced" because of it being strengthened/augmented and "flying" because it seems to be some kind of magic projectile attack.