Actually it's not from any language. Kajiura Yuki (the composer of this song) is often used a made up language for any of her soundtrack song compositions called "Kajiurago". The word itself doesn't have any meaning and all Kajiurago songs is meant for open interpretation.
From AnimeGiga video interview (link above)
Interviewer: What is ｢Kajiurago｣?
Kajiura: This so-called “Kajiurago” is actually a constructed language I frequently use, meaningless language fabricated by myself. It’s only that I arbitrarily named it “Kajiurago”. It’s entirely meaningless.
Interviewer: Not even a bit of meaning?
Kajiura: Yeah. Fabricated only for its pronunciation. One thing is that when I wrote insert songs and other songs for anime, I had initially used Italian, Latin, and the like before. Even if it were a non-Japanese song, for scenes whose meaning I cannot match, to use lyrics not matching the work, I don’t like that.
The Kajiurago lyrics are usually never officially released unless otherwise specified. Most Kajiurago lyric we can find is something people write from what they hear. But for Madoka OSTs, the lyrics are actually an official release, although it's not happen very often.
Almost every song from Madoka OSTs used Kajiurago, and Kajiurago is used in many of her compositions, not only for Madoka Magica and Fate/Zero but also in several other OST like "A Song of Storm and Fire" from Tsubasa Chronicle.