Went and did some searching out of curiosity. First off, it seems the translation is a little off. デル・ハガラース should make Deru Hagaraasu, well, at least that's what I found in Vaelis' text copy and through Google searching.Ephyon wrote:However, before there was something I couldn't fix: "Deru bagaraasu" These are definitely not runes, and following the way Halkeginians chant, this should be the name of the spell shouted at the end, which have so far always been in English (She casts "Air Hammer" immediately after in that way). I just can't figure out what the heck it's supposed to be. She seems to use it in order to propel herself.
Now for actually helping, I'm thinking it's German, but I couldn't find the exact word, which is annoying the hell out of me. Of the little German I know, Der means the, specifically the masculine form (they also have a neutral and feminine version). Though the title ゼロの使い魔 公式アンソロジーコミック 風-ハガラース-魔法の章 leads me to believe it indeed has something to do with some sort of wind.
I'm not even decent in German or Japanese, so me being on the completely wrong language track wouldn't be too surprising.