In Bleach, different languages are used by or to represent different groups. For example, the Bount spells are all in German. Many of the terms referring to/for Hollows are Spanish (e.g. Hueco Mundo, Las Noches). "Pluses" (整 (プラス)) is also an English word, or based on one. Is there any symbolism behind the languages used? For example, "pluses" are benign spirits in the human world while both Hollows and Bounts are bad. Does this have a historical or cultural coincidence or were these just randomly chosen languages?
The reason why the author uses the different languages with different groups is because he feels that will attach uniqueness to that group. In one of his interviews I have read, he stresses that for him, characters are very important and he draws the characters first.
In his interview in Germany, when he was asked the same question he replied as below
"As for the Arrancar, I think that Spanish sounds very passionate and a little erotic, so it matches their wild lifestyle. German sounds cold, harsh and methodic, something that matches the straight-forward methods of the Quincys. I would also like to use French at some point, because it sounds very elegant. But I can't figure out a good way to include it into the story."
So I believe, as I said before, that it is to associate some sort of uniqueness to the characters belonging to a particular group.